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Moses Ludel

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Posts posted by Moses Ludel

  1. masonmoa...The 225 V6 was used in the Jeepster/Commando with a THM400 GM transmission behind it.  That would be one source or method for identifying the correct flexplate.  The other approach would be Buick Special passenger car applications for the 198 V6 and 225 V6 (both odd-fire).  Buick used these engines from 1962-67 in the Buick Special.  THM transmissions were used in the later Buick Special applications.

    Kaiser/Jeep would not have done anything unusual with the 225 crankshaft flange.  There was no need to match any other engine or transmission type.  The 225 Dauntless was purchased from GM in crate form.  This would have involved a GM flexplate for the THM400.  Buick used the THM400 in heavy cars and muscle cars behind 400, 430 and 455 V8s.  The 350 Buick V8 was used in the Jeep J-truck/Wagoneer models from 1968-71 with both manual and THM400 transmissions.

    To your immediate need, I found this flexplate at The Jeepster Man.  It should be what you need if your torque converter will bolt to this flexplate properly.  Explain that you're mating a THM700R-4 when ordering:

    https://www.thejeepsterman.com/products/2514-flex-plate-225-v6-1966-1971-jeepster-commando-cj5-cj6/

    Parts Mike also offers a flexplate but is currently out of stock according to his website:

    http://www.partsmike.com/index.php/products/g106-flywheel-buick-v6-oddfire  [Says "flywheel" in the link but is actually a flexplate.]

    This should put you on the right path.  Let us know if these leads work.  I have additional thoughts if they do not.

    Moses

  2. SomeBuckaroo...Let's start by considering your test patterns.  It's important to separate the roles of the camshaft position sensor (CMP) and crankshaft position sensor (CKP).  The camshaft position sensor, a hall effect signal, is a sync signal generator.  The distributor shaft is gear-driven by the camshaft, and the hall effect pickup (sync signal generator) is attached to the plate below the rotor.  Here are FSM explanations for the roles that the crankshaft position sensor (CKP) and camshaft position sensor (CMP) each play:

    Jeep 4.0L Camshaft Position Sensor Function.jpg

    Above explains the location and signal from the camshaft position sensor...

    Jeep 4.0L Camshaft Position Sensor.jpg

    Above is the Jeep 4.0L (similar to 2.5L) distributor type ignition's camshaft position sensor (the plate below the rotor).  Note that the curved pulse ring in the distributor housing is 180-degrees.  It is attached to the distributor drive shaft, which is driven by the camshaft.

    Jeep 4.0L Crankshaft Position Sensor.jpg

    Above explains the crankshaft position sensor (CKP) role...Shown at right is the 2.5L flywheel with two four-pulse groups.  The flywheel or flexplate attaches to the crankshaft in a fixed position. 

    Jeep 4.0L Crankshaft Position Sensor (2).jpg

    Here is your 4.0L crankshaft position sensor (CKP) with three groups of four pulses (a hall effect like the camshaft sensor).  The flywheel rotates and the CKP sensor sends a signal to the PCM. The crankshaft position sensor mounts at approximately 11 o'clock when viewed from the transmission.

    So, your camshaft sensor's scope pattern is the pulse signal generated to help time the fuel injectors.  By contrast, the crankshaft position sensor (CKP) is a consistent signal to the PCM that pinpoints TDC for #1 piston.  The square waves (shown on your scope overriding the spark firing lines) is the camshaft position sensor signal with its 180-degree pulses.  (For correct spark and injector timing, it is necessary to install the ignition distributor exactly like described in the FSM.)  The camshaft signal may be confusing.  This signal is not intended for referencing the #1 cylinder's piston at TDC.  The TDC signal comes from the crankshaft position sensor.  The camshaft sensor feeds information to the PCM for sync'ing the injector firing points at the cylinders.  The PCM determines spark timing with data from the CKP, CMP, O2, MAP and other sensors. 

    Note:  It's easier to get the #1 cylinder firing trigger from the #1 spark plug lead, using your capacitive/induction clamp attached to the #1 spark plug wire.  We're using this trigger to identify the firing order.

    Clamping to #1 spark wire provides a rough TDC reference with #1 piston near its firing position. Base timing is not fixed or constant with electronic fuel-and-spark management.  (There is negligible deviation in valve timing or the distributor shaft position with the engine running.)  What you see as the #1 cylinder spark firing line represents the degrees of spark timing advance.  The amount of advance is a PCM function.  Spark timing reflects PCM algorithms based on the engine's sensor feedback.  With EFI management, we usually see 12-14 degrees spark advance in an unloaded, idling emissions engine.  That's close enough to get a firing order reference.  Actual piston location would need a CKP or CMP pickup.  CKP would be slightly more accurate than the CMP.

    If you probe the crankshaft position sensor for a #1 cylinder TDC reference point, the 4.0L (six-cylinder) flywheel generates three groups of pulses for each revolution of the flywheel.  The crankshaft rotates twice for each 4-stroke cycle of the engine.  (The #1 piston reaches TDC at the top of its compression and exhaust strokes.  It takes 720 degrees of crankshaft rotation to complete the 4-stroke cycle.)  The crankshaft is a steady rotational reference with the flywheel rigidly attached to the crankshaft.  Despite the accuracy in finding "true" TDC, it's easier to get a #1 spark lead reference to determine the firing order. 

    Footnote:  For ignition diagnostics on a distributor engine, we have always used #1 spark lead for the firing order reference and probed the coil high tension (secondary) lead to parade firing lines for all cylinders.  (Primary ignition patterns, dwell angle and breaker point condition are a separate signal on breaker point era scopes.)  Traditionally scopes have an induction clamp for #1 spark wire and a clamp for the cap-to-coil high tension secondary lead.  The secondary coil lead provides the full parade of cylinders while the #1 spark lead triggers the firing order.

    The two scope methods for running a "relative compression test" are 1) the starter motor cranking draw and 2) the exhaust pulse sensor readings with the engine running. Your pressure pulse and vacuum readings are sharp and clear.  Yes, there is some irregularity at both the intake and exhaust pulses per cylinder, which could explain the rough idle.  However, to once again separate mechanical from fuel/spark related causes, a cranking (starter motor) amp clamp test would be helpful.  We're close but still not completely there...

    A cranking relative compression test is quick and easy to run.  You can begin by either attaching a remote start switch at the starter motor (keeping the ignition/key switch in the OFF position) or removing the fuel pump fuse or relay.  Either approach will prevent the engine from firing.  However, I still crank the engine for a moment when using the key switch with the fuel pump fuse or relay removed.  This will eliminate a hiccup or hot false start due to pressurized fuel still in the EFI/MPI fuel rail.

    Something like the Innova 3630 remote starter switch at AutoZone ($8) will do the job.  (There are more robust remote start switches available if you intend to use the remote switch regularly.)  The 4.0L Jeep starter relay at the starter motor is easy to access for attaching a remote start switch.  The remote start switch closes the Jeep 4.0L starter motor's relay and engages the starter motor directly at the starter.  Again, be sure to keep the ignition key switch in the OFF position while you attach and use the remote start switch for this test.  You want to crank the engine without starting it.  The amp clamp will still pick up the starter motor draw from the battery cable.  

    Clamp around the battery cable running to the starter motor.  (Since this is D.C., you can pick up this signal with the clamp around the negative battery ground cable if preferred.)  By removing the fuel pump fuse or relay, you can turn ON the ignition switch with the scope's capacitive induction clamp hooked to the #1 spark cable.  The induction probe clamp at #1 cylinder spark lead can serve as the trigger pickup for identifying #1 cylinder in the firing order.  

    Caution:  Automotive scope capacitive induction pickup probes are intended for secondary voltages.  However, as a rule of thumb for any directly applied high voltages, use an attenuator if necessary to protect your scope!

    The cranking voltage changes from the amp clamp on the battery cable will indicate the amperage draw for each of the six cylinders.  Any variance in a cylinder(s) is the relative compression difference.  A higher amperage draw reflects higher compression (more piston resistance on the compression stroke) in that cylinder.  Lower amperage draw is a weaker cylinder.

    Simultaneously, with your four-channel scope you should be able to get a read of intake or exhaust pulses during cranking.  (The engine/flywheel is rotating at 180 or so rpm while cranking, which should be plenty.)  There should be adequate intake air flow.  Consider wedging open the throttle during this test to assure air flow volume.  

    For more about this relative compression test and the amp clamp, check out the first three minutes and twenty seconds of the tune-up video I did for the magazine:

     https://4wdmechanix.com/jeep-4-0l-ignition-tune-up-and-injector-cleaning/

    An accurate pattern occurs as the starter current stabilizes.  With the battery fully charged, I usually run a cranking compression test cycle for 5-10 seconds (maximum) and record with the scope.  You'll see from my video that there is initial voltage irregularity as the starter motor engages the starter ring and overcomes inertia.  Simultaneously capture intake or exhaust pulse readings while cranking.  The tailpipe pulses will not reflect combustion but instead the piston and valve movement that creates vacuum and pressure changes during the intake and exhaust strokes.

    With a #1 cylinder reference, you can follow the 1-5-3-6-2-4 firing order and align the parading cylinders with the pulse sensor readings.  If you can get distinct intake vacuum and tailpipe pressure readings while using your pulse sensor at cranking speed, it would be valuable to align and compare the pulse sensor readings with the starter draw's "relative compression" pattern.  We'll look at your findings. 

    Below is an introduction to the Autel scope with the accessories kit.  At 5:08 to 5:58 minutes, I show the amp clamps that are included with the Autel MP408 Oscilloscope Accessories Kit (OAK).  You will recognize the clamps as similar to Hantek:

    Also, here's what I did with my pressure pulse sensor.  I improvised a cone to somewhat "channel" the exhaust pulse inside the tailpipe.  I'm not clear whether this improved my pulse readings.  Your readings look good.  Perhaps the cone is unnecessary.  It's worth experimenting:

    20230311_193223[1].jpg

    20230311_193300[1].jpg

    From what I see in your patterns, there is intake idle vacuum and tailpipe pressure irregularity.  The test of relative cranking compression simultaneous with vacuum or pulse tests would help pinpoint a mechanical problem (poor valve seating, compression blow-by, etc.).  If relative compression is rock solid and uniform while these vacuum and pressure pulses act erratically, there could be a fuel/spark or vacuum leak issue.  (Is the exhaust manifold/header leak free?  The slightest leak can dilute the O2 reading and create a fuel trim issue.  These manifolds are notorious for cracking and warping.)  Of course, to eliminate any questions about mechanical issues, your in-cylinder pressure transducer kit will be the ultimate diagnostic tool.  Excited to see your findings!

    For now, should you discover uneven relative compression that aligns with these vacuum and exhaust pulse fluctuations, use your pulse sensor at the dipstick tube.  Engine idling, any pressure fluctuations in the crankcase would indicate a mechanical issue, most often compression loss from piston ring blow-by.  This is how we separate valve seepage and valvetrain issues from ring blow-by when running these tests.  The dipstick tube pressure pulse can also be a follow-up for a low compression reading with the in-cylinder pressure transducer.

    Moses

     

  3. Doug3...You're on the right track by priming the engine before running it...Make sure the rocker arms move freely and the valves open-and-close properly. I would start priming with #1 piston at TDC on its compression stroke; rotate the crankshaft 90 degrees and prime again; then rotate the crank to 180 degrees, prime again; then rotate to 270 degrees, prime again; then rotate to 360 degrees. (#1 piston is now at TDC on its exhaust stroke.) 

    Prime at TDC of the exhaust stroke and repeat the 90-, 180- and 270-degree priming, bringing the crankshaft back to TDC for #1 piston on its compression stroke.  Align the oil pump drive as you drop the distributor back into the engine with the rotor pointed to #1 spark lead of the distributor cap.

    At one or several of these priming points, you should get good oil flow at each rocker shaft.  Make sure the rockers open and close freely while performing these steps.  Let us know if this solves the oiling issue.  If not, share whether any work appears to have been done to the top engine/valvetrain (rocker shafts, rocker arms, etc.).

    When ready to start up, I'd run fresh oil and a quart of Rislone Engine Treatment with a new oil filter.    

    Moses

  4. Julio...The VIN does not indicate the fuel tank type on your YJ...I looked at the eBay link, that module is listed for a "15-gallon" tank.  There is also another Crown offering that has a few more parts:  https://www.ebay.com/itm/392125484356.

    As for fit of the Crown module, a reviewer notes that his fuel pump/gauge module has a square (rectangular) top, not the round top shown in these eBay illustrations.  18 years ago, I replaced the 14.5-gallon OEM tank in my son-in-law's 1987 2.5L Wrangler with a 20-gallon tank.  Both tanks had square (rectangular) module flanges held down by a set of threaded bolts or screws.  The 14.5 and 20 gallon tanks are distinctly different widths/shapes and easy to spot.  (See my photos below.)  You should be able to look at your tank and identify which type you have in your YJ:

    101270.jpg

    Above is the original/OEM 1987 YJ Wrangler 2.5L 14.5-gallon tank.  Note that the left and right sides are square and even with the skid plate's width.  The tank was poly plastic (HDPE) and had a loose tailpipe scorch that the previous owner neglected.

    101271.jpg This is the 20-gallon replacement tank (used) that fits the 1987-95 YJ Wrangler.  The new fuel pump/gauge module is an OEM Mopar replacement unit for the 20-gallon 1987-90 YJ Wrangler with 2.5L TBI engine (the lower pressure pump).  Note the width and shape of the tank.  It is HDPE "poly plastic" with a rectangular flange at the top of the pump/gauge module.

    101273.jpg

    This is the top of the OEM 14.5-gallon tank.  I'm unhooking hoses and about to remove the square/rectangular flange hold down plate that secures the fuel pump/gauge module to the top of the tank.

    101272.jpg

    Here, the original fuel pump/gauge module comes out of the 14.5-gallon tank.  Note the flange is square/rectangular as the eBay reviewer stated—not round.  The thick flange gasket is rectangular.

    101274.jpg

    This is the 20-gallon tank from a recycling yard.  It is HDPE (plastic) with a rectangular fuel pump/gauge module flange.  As I recall, this tank was 1991-95 era but looks just like the 1987-95 20-gallon plastic tank listed at eBay:

    https://www.ebay.com/itm/283933653422

    Morris 4x4 Center sells both the MTS and Crown 20-gallon replacement tanks.  Each has the rectangular flange:

    https://www.morris4x4center.com/gas-tank-20-gallon-polyethylene-plastic-52018287.html

    https://www.morris4x4center.com/crown-fuel-tank-and-skid-plate-master-kit-20-gallon.html

    So, it looks like these "Crown" fuel pump/gauge modules have a round flange and will not fit your YJ if the flange is rectangular like these examples.  There are aftermarket metal fuel tanks with round module flanges that use a lock ring.  So does the XJ Cherokee.  These pumps may fit that kind of tank...Avoid any fuel pump listed for a 1991-95 YJ Wrangler.  It will be an MPI 2.5L or 4.0L pump with a high pressure rating.  Although these pumps fit up to the tank, they have way too much pressure for a 2.5L TBI system.

    I would get beneath your Jeep with a small inspection/extension mirror and see if you can view the top of the tank.  Determine the width and shape of your tank (14.5 gallon versus 20 gallon).  Inspect the fuel pump/gauge module's flange shape.  The rectangular flange has screws or bolts securing it.  The round flange types have a lock ring.

    A complete fuel pump/gauge module can get expensive, the reason that many just replace the pump.  Unless the fuel gauge is not accurate, replacing the pump is usually enough.

    Let us know what you have for a tank and the flange type...

    Moses

  5. Julio...Yes, this is an unusual thread size for a fitting.  The port is normally used with the Mopar pressure gauge kit, which is not a common thread.

    So, good, you're getting somewhere with the fuel system diagnosis and enrichment issue.  Here are the original 2.5L TBI part numbers from Mopar.  A factory NOS pump could be difficult to find, this is just for reference:

    83502994  PUMP PACKAGE, Fuel - TBI 2.5L Eng. with 14.5 gallon fuel tank
    33000184  FILTER, Fuel - 2.5L Eng.

    83502995  PUMP PACKAGE, Fuel - 2.5L TBI Eng. - U.S., Canada and ECE with 20 gallon fuel tank
    33000184  FILTER, Fuel - 2.5L Eng. - U.S., Canada and ECE

    For aftermarket fuel pumps of the correct pressure, below is the popular Crown Automotive replacement pump.  The Crown 83502995 is a replacement for both the 83502994 and 83502995 Mopar pumps.   As you know, the main thing is to get the correct (lower pressure EFI) pump for the 2.5L TBI system. 

    This is just the fuel pump and not the entire fuel module with pump, gauge, etc.  The 33000184 filter is not the frame rail filter.  This is the filter at the bottom of the fuel pump inside the fuel tank.  It is not included with the Crown fuel pump kit:

    https://www.crownautomotive.net/Fuel-Pump-Kit/83502995.html

    https://www.summitracing.com/parts/cwa-83502995  [an additional source for the Crown pump]

    Before investing in a new pump, make sure there are no restrictions on the return line to the tank.  Also, determine whether you can adjust (lower) the fuel pressure at the regulator.  You could not find an adjustment screw.  Let me know if that's still the case.  There are other ways to lower the pressure.  18-20 psi is definitely too high and could be causing the rich running condition.

    Moses

  6. Exciting, SomeBuckaroo!...Pleased that you purchased the in-cylinder pressure transducer and reliable probes.  We could see the spark cable/high tension cable noise with the Hantek cables.

    For an accurate picture of cylinder pressure(s) and how they relate to a rough idle, you can 1) back probe the Crankshaft Position Sensor to set a true TDC for #1 cylinder and 2) probe the #1 spark plug cable to show #1 cylinder firing and identify which stroke the piston is on.  If you parade the firing order on one channel and the in-cylinder transducer on another, you can look for a relationship (if any) between the idle roughness and the test cylinder's running pressure changes and compression. 

    Since your scope has four channels, you can probe the crankshaft position sensor on one channel, clamp #1 spark cable on a second channel, use the in-cylinder transducer on a third channel and use the fourth channel to probe the camshaft position sensor.  (Select and set up the channels as you want them to display on the scope.)  Variations between the crankshaft position and camshaft position will indicate any timing chain slack.  The camshaft position probe will also help match up the camshaft degrees with the cylinder pulses.  We can discuss camshaft/valve timing, lobe wear and lifter issues if you see fluctuations between the tested cylinders.  The camshaft, lifters and chain are new.  There should not be an issue here.

    Since the #1 cylinder (or whichever cylinder you test) will not have ignition with the in-cylinder transducer in place, you are strictly looking at fluctuations in real time pressures within the cylinder.  Since the cylinder is not firing, there will be no combustion effect or analysis.  You are isolating and testing the cylinder's pressure changes, not the combustion process.

    For a look at ignition function while you test cylinder pressures, a spark plug simulator can test the spark cable and ignition function with the engine running.  This will demonstrate ignition performance while you run the in-cylinder pressure test.  It will also prevent damage to the ignition...Example of a spark plug simulator:

    https://www.amazon.com/Stens-750-018-Ignition-Designed-exclusively/dp/B001OK6MIO/

    You may discover mechanically caused roughness (like poorly seating valves) as you test each cylinder.  If the valves are not seating or there is irregular piston ring seal, you will see fluctuating, unstable pressure readings.  In any case, while you test a cylinder, the 4.0L inline six engine is running on five cylinders.  The purpose of the test is to discover abnormal pressure pulses and determine peak (ready to fire) pressure in the cylinder.  I would run the test at each cylinder, record the findings or save screen shots.  Compare the cylinder readings.  The highest pressure cylinder is often your benchmark.  

    The in-cylinder compression test will illustrate variations in intake or exhaust stroke pulses, show the compression pressure rise on the compression stroke, and pinpoint the maximum pressure or any pressure fluctuations in the live cylinder.  At normal idle speed (which the IAC should establish even on five cylinders), you will be observing 720 crankshaft degrees (two rotations of the crankshaft) to complete the 4-stroke phases.  The crankshaft will be turning 650-700 rpm.  Set your time interval readings to provide a clear, six-cylinder firing parade across the screen.  Then zoom into a view of just the test cylinder.

    If pressure pulses match per cylinder and compression is nearly equal and sufficient per cylinder, with no signs of valve leaks or wide differences in peak compression, the roughness is likely tune, O2, MAP, IAC, fuel trim, injector, vacuum or air leak (intake or exhaust) related.  We're speculating for now.  Your pinpoint test tools are coming!

    Moses

  7. Hi, Don (cajuntracker)...Knyte is right, for your sake, we'd prefer assisting here at the forums.  The Tracker and Sidekick powertrains are similar.  Do you have a particular repair or troubleshooting need?  Are you seeking a replacement engine for either a Tracker or Sidekick?  Are you updating an early model with a later engine?  Please share information.  We'll assist if we can...

    Moses 

  8. Very helpful comments, Bill W.  I will talk with the SpynTec folks to qualify their rationale for a bearing preload.  Could be liability, service simplicity (no dial indicator involved) or an equivalent to rear full-floating axle hub bearings.  I'll update.

    I will check the ball joints and certainly replace them as needed—or maybe as a preventive measure.  Best to do it with the other work underway.  Likely Spicer would be my pick.  Another 190,000 miles of service is reasonable. 

    Upper joints are usually greaseable.  On 4x4s, the lower U-joint is permanently sealed.  An exposed grease fitting could be damaged off-road.  (Spicer/Dana lower ball-joints have a tough base.)  The plug and needle greasing approach works although shops resent and avoid  the two minutes of extra work.  That's why I've always done my own maintenance!

    We'll keep each other posted.  Great to share this information!

    Moses

     

  9. Hi, Bill...I read your reply and very much enjoyed it!  See my comments:

    On 2/13/2023 at 11:32 AM, Bill W. said:

    Good morning Moses. This reply is in the same order as my original post so it will have some continuity. 

    The NV5600 transmission is a beast for sure. Weighing nearly 400LBS, one must be prepared to remove it. The gear ratios are very evenly spaced and I have never wished one was a little lower or a little higher while going through them. It is a little difficult to shift however. Finding the gates, learning the springs in the shifter, and the exact lever travel took me a little practice and I sometimes still have trouble.  Once in a while I get a little gear clash but mostly when cold. It cannot be shifted fast at all and would never win in a drag race. I didn't buy my rig to go fast. I have other toys for that. I have no personal knowledge of the G56 but from what I have read, its tow rating is lower and when subjected to heavy loads the aluminum case has a tendency to spread causing cracks or breakage. A steel girdle can be fitted to help stiffen it but I don't know of the effectivity. It is probably a good transmission that shifts easily and precisely and works well for a daily driver and light duty use. You may be better off with the 7 speed!

    Are we old school iron case aficionados?  (Carryover from the SM420, SM465, NP435, T-18/19 days?  Maybe the basis for my fascination with the Spicer and Eaton 7-speeds?)  I'm also skeptical about the G56 and have heard the same comments about its aluminum case.  I just finished filming a video series at Advance Adapters, and the current rage for Jeep® and lighter 4x4 conversions is the Tremec TR4050, an aluminum case direct replacement for the NV4500 5-speed (the gasoline engine version).  40 pounds lighter and 600 lb-ft rated.  Ideal for a light vehicle without a horse trailer in tow.  For good reason, our Cummins 5.9L H.O. engines are not on the application list for this transmission.  (The '05 rated 600 lb-ft torque stock.  My Hypertech Max Energy Stage 3 tune added a conservative 50+ extra lb-ft and keeps me light on the throttle during upshifts with a trailer in tow.)  Tremec does not offer a Cummins style 1-1/4" input shaft. 

    Note: Some upgrade the Dodge/Cummins NV4500 to an aftermarket 1-3/8" input shaft and South Bend clutch.  The currently available TR4050 is for gasoline applications only.  If an input shaft were available, it might work in place of a Getrag 360 behind a stock 12-valve Cummins.

    I have no regrets converting to free spin front hubs. Since I was facing a forced decision in a replacement, I wanted to spend good money once and have a serviceable hub rather than continue with the unit bearing and a chance to increase my mpg. In just about everything I do, I research, evaluate, consider the cost and make a decision. I chose SpynTec and used Mile Marker stainless steel hub locks. The SpynTec hubs are a quality piece and came with a very durable plating that shows no sign of rust since I installed them in 2017. I went with MM instead of Warn because of the cost. So far in their limited use I haven't had any trouble with the MM. In getting the knuckles apart and changing the ball joints, I couldn't find anyone that had a ball joint press to rent or the other tools required so I bought OTC kit 8031. An unexpected expense but I still came out ahead since I did all my own work. As for ball joints I went with Dynatrac. Carli makes some nice ones also but more expensive. I would warn other readers to make due diligence on replacement ball joints. I stayed away from Moog, Napa and another I can't remember because some are oversized or knurled and when they wear out... good luck. The Dynatracs are also rebuildable. Now I have an all new front end including U-joints. I would be interested if you find better braking with the hubs as I did.

    Very helpful feedback.  I'm in a conversation with SpynTec® and like their engineering and materials.  In the installation instructions, I find it interesting that SpynTec® adjusts the wheel bearings to a preload rather than an end play.  Jeep® CJ and closed knuckle axles did this, but the open knuckle light truck 4x4s with a Dana 44 or 60 front axle called for front wheel bearing end play.  Following the adjusting procedure, the final settings were 0.001"-0.010" end play, which we checked with a dial indicator.  As a GMC light truck dealership tech in the early eighties, I set K-model straight in-and-out end play at 0.002"-0.004" (maximum) with new or pre-run bearings, using quality heat-resistant grease.  Do you use the SpynTec® adjusting method?

    Thanks for the heads up on Dynatrac "rebuildable" ball-joints.  Did your truck need ball-joints or was this an elective upgrade?  At 186K miles, my truck's ball-joints may show their age, and the free-wheeling hub install would be an opportunity to replace them.  I also avoid knurled (oversized) ball-joints for a first round ball joint replacement.  Oversizing would be a last resort for badly corroded knuckle bores (after clean-up) or for a second time around ball-joint replacement.  Even then, I'd try standard size joints first.  For stock replacement, I generally use Spicer ball joints.

    I am well aware of automatic locking differential behavior.  I have a couple of cars with them and my '79 Ford with the 460 had a locker in the back. It was a purpose built rig and a wheeling machine. A lot of fun! My Dodge is not a wheeling machine and I did not buy it for that. If I had the factory posi I would not have changed it, I don't think. But since it was open and I had been in several situations where I had to engage the front just for an easy task where my Ford would march on without missing a beat, I went with what I could afford and a proven brand. All of my lockers are Detroit. Did you look for the ID sticker in your glove box for the diff gear ratio? Just curious.

    I have the OEM rear locking differential, it's been trouble free to date.  I would consider a manual or electric locker if available.  Your Detroit should work well.  My Gen 3 3500 SRW came with 3.73:1 axle ratios, AAM 11.5" full-floater rear/AAM 9.25" front.

    Hearing about your idea for the school is very interesting. Especially for differentials, I believe the tooling is a big obstacle for most including me. Torqueing the ring gear bolts on the AMM 11.5 was tough! I had my wife put the trans in first gear low range to keep the ring gear from turning while I torqued the bolts. Anyway, I will look for the notification of the launch date. And I will look at the site.

    I'll keep your two axle "pain points" in mind for the course:  tooling and setting torque.  Yes, OEM tools are expensive, I have the factory pinion depth/height setting tools (Miller/SPX) for all popular Dana axles plus our AAM Ram and similar GM trucks.  Frankly, cost for this coverage would be prohibitive for most shops.  Fortunately, there are contemporary "universal" pinion height tools available, and some work easily and well.  Pullers and a press are other expenses that could be an obstacle if only used for one axle build.  This pending course will likely attract shop techs and DIY mechanics who know there will be more than one axle build or service ahead.  The course goal is to raise confidence and ensure that any axle project can produce safe, reliable performance and predictable results.

    Lastly the tires. I may have to resign myself to stay with the same size I already have of 295/70-17 and drone along at 65. Unfortunately when I see other Dodge diesels with bigger tires and ask them what they think and mileage etc, not many have specific mpg reports. Either the lie-o-meter or a best guess. Since this thread is about mpg, I want to be able to report back with my accurate findings for the benefit of others seeking the same. Thank God for cruise control.

    Yep, cruise control improved mpg on the recent trip to Paso Robles.  I "kept up with the traffic" on I-5 through the Valley on the way down.  Result:  16 mpg at 72 mph.  On the way home, holding 65 mph with the cruise set netted closer to 20 mpg (43 miles of chain control over Donner Summit curtailed the fuel mileage test!).  295/70-17 would be my peak height (approximately 33.3" diameter) for the 3.73 gears.  You have the best balance between performance and mileage without a chassis lift kit.  The gearing will still pull a trailer, and you can keep a lid on the engine rpm for fuel efficiency.

    Keep us posted!  Best...

    Moses

    All the best,

    Bill

     

     

     

     

  10. SomeBuckaroo...I really like the spark plug condition and burn!  NGK is among my favorites, I run NGK on all my dirt Honda XR motorcycles and most often in the 4.0L Jeep six.  While the bikes (carbureted with a wide altitude range of riding) do better with iridium style plugs, that's not a necessity for your 4.0L Jeep application.  The current V-Power replacement plugs are doing a great job. 

    There is some wear on the center electrode tips but unless you want to replace these plugs due to mileage, they should still be firing okay for now.  (Check and compare resistance with your ohmmeter if concerned.)  Likewise, the TPS on order could be held as a backup until the Mopar TPS gets symptomatic, a matter of time.  For guaranteed idle stability, the TPS and IAC valve need to perform consistently...Your call.

    As for your deep dive into firing line voltages and the snap throttle experiment, see my comments below in red italics...Nice work here, I like your scope adjustments and attenuation in order to see the full spark line heights.

    4 hours ago, SomeBuckaroo said:

    I captured a video of the entire spark parade during several throttle snaps:
    https://youtu.be/y4Rm8htZ660

    Watched the video several times, very helpful.  Did you change the cap and rotor before this test cycle?  There's nothing extraordinary or grossly troubling.  The spike heights are normal, created as load increases and cylinder pressures rise with the quick/snap throttle opening.  As the throttle closes, the lines drop below the idle baseline then fluctuate as the idle restores, all of which is normal. This is a reduction in engine load/cylinder pressure plus the fuel injector, fuel trim and ignition timing functions (essentially the EFI "fuel-and-spark" engine management)—again, nothing alarming.

    On older carbureted engines, the closing throttle and immediately after the snap would show enrichment (lower spark lines) due to the "venturi effect" within the carburetor. With venturi effect, while the closed throttle does not call for added fuel, it gets fuel anyway. Aside from no load and dropping cylinder pressures, the richer mixture ratio fires easily with less voltage resistance, and this reduces the amount of spark voltage needed.  The spark firing lines are shorter.  By contrast, EFI can cut off fuel as soon as the throttle shuts, eliminating richer mixtures during deceleration and throttle closure.

    I took rough measurements of firing spike heights. My Hantek HT25 probes attenuate by 10,000:1; I configured the scope such that each major vertical division represents 5,000 volts. I tried to set a cursor (horizontal dashed-line) to be helpful, but realized after the fact that it was not placed quite right. Regardless, here's measurements from several frames of the above video:

    Spark Firing Spikes (Kilovolts)
    
    "Idle 1" and "Idle 2" are measurements taken during idle
    "Snap 1" through "Snap 3" are measurements taken during brief throttle snaps
    "Max diff" is the maximum difference between lowest & highest cylinder (KV)
    
    Cylinder | Idle 1 | Idle 2 | Snap 1 | Snap 2 | Snap 3 |
    1        |   18   |   21   |   16   |   16   |   16   |
    5        |   17   |   17   |   15   |   15   |   16   |
    3        |   17   |   17   |   14   |   13   |   21   |
    6        |   18   |   28   |   14   |   15   |   15   |
    2        |   16   |   24   |   15   |   17   |   17   |
    4        |   21   |   22   |   15   |   15   |   15   |
    Max diff |    5   |   11   |    2   |    4   |    6   |
    

    Your attenuation and visible patterns are well done...The most reliable read of the snap throttle was your first one.  The time between the snaps was too short; the engine management needed to stabilize.  If you monitor fuel trim with your scan tool at the same time, you'll see what I'm suggesting.  Allow the engine idle to completely stabilize between each snap test.  As for your results, I see this differently.  Watch closely:  The snap causes an instant increase in the voltage demanded;  the lines increase in height at the snap.  This is due to cylinder pressures ramping up and the added firing voltage needed to provide adequate spark.  

    Generally, my observations are that the spikes are significantly lower during a throttle snap than at idle. They also appear to be somewhat more uniform in height during the throttle snap than at idle. I can't really discern any characteristics of each particular cylinder - the spikes seemed to all vary a lot regardless of cylinder.

    The other way around:  Snap raises the lines.  You're catching the rebound as the throttle closes, which drops the spark firing voltage below the normal idle voltage.  At an idle, the system quickly restores to the idle spark voltage.  Can you stretch out the scope pattern to reveal a wider view as the spikes occur?  Or can you stretch out time in your video software edit (create "slow motion") while keeping the audio active and in sync with the stretched video track?  The audio will sound slow and drawn out, but it will align with the spark firing line positions.  This might be easier to follow.  I know what to expect at the snap, so it's easier for me to discern that the lines go up.

    To be clear, the spark or firing resistance goes up during the snap.  Therefore you see the lines momentarily shoot upward.  The drop in firing line heights when you unload the throttle reflects either lower firing resistance or momentary fuel enrichment—or both.  Review your video or play with this more.  

    In general, a lean mixture will raise the spark firing lines because a lean mix requires more voltage to fire.  A relatively richer mixture fires more easily. The baseline for optimal gasoline combustion (stoichiometric) is 14:1 Air/Fuel.  For emissions purposes, modern EFI engines are tuned to run as lean as possible except when accelerating (wide open throttle or WOT) or when under load.  For adequate performance, a balance gets struck between spark retard to prevent detonation and optimal fuel mixtures for meeting tailpipe emissions requirements.

    To see this at work, read your lines with the engine first idling cold (enrichment cycle) in O2 sensor open loop mode and below 140-degrees F coolant temperature.  Spark firing lines may be lower than when the engine is warm and in closed loop.  This would reflect a slightly richer mix or what a "choke" once did on carbureted engines.  Since you have baseline "normal" idle spark firing lines established, see whether this holds true.  The wild card is that cold spark plugs and cylinders create resistance to combustion, so spark voltage requirements and firing lines may go up.  Try this, anyway.

    I had considerable difficulty reliably triggering on Cyl 1, so I am considering using the camshaft position sensor signal (CMP) to trigger since it ought to be less noisy than the capacative pick-up of Cyl 1 plug wire. I will first capture CMP and Cyl 1 spark to establish & document the timing relationship.

    That's a good idea.  You'll be at a fixed #1 cylinder timing line that aligns with the distributor shaft.  This should be relatively close to TDC at the crankshaft.  The engine is nearly new with a new timing chain and sprockets.

    For additional info, I hooked up my timing light - and found idle timing "off-scale" BTDC: the timing mark was further BTDC than the extent of the scale on the timing cover, and was often nearly obscured by the fan pulley. The timing also jumped around considerably. I verified with my OBDII scanner that the ECU indeed reported approx 18* BTDC at idle (so the harmonic balancer hasn't significantly slipped on its rubber isolation ring). Is this timing advance and erratic behavior expected? I took a video showing the timing mark's behavior at idle (I used a red paint-pen on the crank pulley scribe, and I marked up the video with a white arrow pointing to the action):
    https://youtube.com/shorts/xYFxykaLYQw

    This is all very normal for electronic fuel and spark management.  If your crankshaft position sensor, MAP, O2 and other sensors are feeding information correctly, the engine is attempting to minimize emissions while in an unloaded condition.  Advanced timing raises manifold vacuum...Under normal conditions, with the engine loaded in Drive with an automatic transmission, the idle timing advance would change.  Overall, the PCM has spark timing curve algorithms the are constantly changing with sensor input.  The spark timing curves are unlike the fixed curves in conventional distributors.

    Our 1999 4.0L sixes do not have a knock sensor and rely on sensor-fed information and fuel-and-spark management programming to prevent detonation/ping. Our distributors set in a fixed position.  (There is no provision for "adjusting the base timing".)  The distributor housing and rotor/shaft each index in fixed locations.  The PCM gets a #1 cylinder TDC reference from the crankshaft position sensor.  All timing adjustments and changes take place electronically. (There are no centrifugal or vacuum distributor advance mechanisms!)  The rotor and cap contacts feed spark to the plug wires while the degrees of advance and retard get assigned by the PCM...2000-up Coil-On-Plug engines eliminate the distributor altogether.  Spark is triggered directly by the PCM to a coil at each cylinder.

    Moses

     

  11. SomeBuckaroo...This is the oscilloscope vantage you needed.  Great scope settings and photos!

    The spark firing lines look reasonably even.  Regarding the spark firing lines within the firing order, there is some variation.  To make sense of whether this is an acceptable range, please share the voltage readings for peak spike height per cylinder in the firing order.   Firing heights and resistance/voltage do not seem grossly different per cylinder, but we're keeping your rough idle symptom in mind.  What is the lowest versus the highest voltage reading per cylinder? 

    Also, blip the throttle and watch where the spark firing lines go.  Watch this carefully and note the height of the firing spikes.  See whether they remain somewhat uniform height.  Keep the valve fluctuation in mind (i.e. compression and combustion efficiency as reflected in the spark firing lines).  See whether an engine speed change reveals signs of poor combustion.  Resistance (spark lines) should go up with the snap throttle, but do the firing lines rise uniformly?  You will need to lower your screen view to see these changing spark line heights.  The spark firing lines are high kilo-voltage readings.  Set the scope for accurate and clear readings at this voltage.  You'll be viewing six-cylinders simultaneously in parade.

    This viewing should align with your leakdown and compression checks.  Your spark cables do meet OEM/FSM resistance range (3,000-12,000 range ohms per foot).  From what I see, there's no reason to suspect a fuel injector issue, which you verified with the fuel trim readings.  The oscilloscope has provided another dimension to the overall tune "picture" in real time running state.  Very valuable.

    As for the cap and rotor, they're a mess and need replacement.  If these pieces are still apart, I'd also like to see the spark plug tips with the plugs laid out in their cylinder order.  Measure the spark plug gaps and note the oscilloscope spark line and coil oscillation view for each spark plug in the firing order.  This is the kind of insight a scope provides.

    Regarding how to "read" the spark firing lines, this is a tradition look at how an ignition functions:  1)  The high spike is the spark plug firing; 2) the relatively straight or up-sweeping jagged line is the spark firing duration and dissipation; 3) the squiggly extended line is the ignition coil oscillation and 4) the long, flattening line is the "dwell" period for when the coil builds voltage for the next cylinder to fire. 

    There is a slight irregularity, though not an "Ah, ha!" moment, in your latest scope reading.  The firing line height and duration of the spark can be impacted by the spark plug condition and the spark plug gaps.  Wider or narrower spark plug gaps will affect the height of the firing line (reflecting the degree of resistance).  A lean or rich fuel mixture will also affect the height of the spark plug firing lines.  This reflects the combustion efficiency, which can suffer from fuel injector issues, a dirty or sticky idle air control valve, an erratic Throttle Position Sensor, a clogged exhaust or cat, or abnormal fuel trimming. 

     I don't sense a glaring mechanical issue like intake/exhaust valves unseated or not sealing.  From the oscilloscope vantage, we're only seeing combustion efficiency, read as spark resistance, i.e. the height of the spark plug firing lines.  This screen view is not a mechanical assessment, yet it provides an insightful look at the running engine's ability to provide compression and normal combustion.  The obvious tell all with the oscilloscope would be running an in-cylinder pressure transducer test of the running engine.  You would test the in-cylinder pressure, preferably at each cylinder, and compare the results, looking for telltale scope pattern differences between cylinders.  This would be the oscilloscope test for accurate valve timing events and valve seating.

    On that note, in-cylinder pressure transducers can be expensive.  Pico and others make them.  Your scope would likely work with any transducer, which simply converts pressure changes into voltage readings.  The in-cylinder transducer must have a fast read/ms rate and enough accuracy to pick up the four-stroke phases of a running engine.

    A far less expensive alternative is a tailpipe pulse pressure test with a pulse tester.  I bought the CRUZ pulse sensor at eBay, and it works:  https://www.ebay.com/itm/184415845508

    At the eBay sales page, the British Columbia seller provides a photo of the device reading a running engine from the tailpipe.  You'll see how useful this pressure pulse sensor can be for determining exhaust pressure pulses.  (Another scope channel can pick up #1 cylinder firing as a marker for identifying the pulse waves by cylinder firing order.)  With your concern for valve seating or spring issues, this would be a vital tool and alternative to the more expensive in-cylinder pressure transducer.

    I red highlighted (above) some tune and idle related items to consider.  The idle air control valve and its throttle body port get clogged over time.  This can be an inexpensive service item at Amazon.  (Read reviews.  I installed an off-shore IAC valve on the XJ 4.0L that  has held up so far.  Buyer beware, though, we get what we pay for.)  TPS is another duty cycle item that affects idle smoothness.  At your TJ's mileage, I would replace the idle air control valve, clean the port in the throttle body and consider the age/mileage on the TPS.  NTK makes a quality TPS at a reasonable price:

    https://www.amazon.com/gp/product/B07F48C2RS/

    The scope is formidable and less expensive than a high end scan tool.  The two tools in tandem make troubleshooting and diagnostics simpler and far more accurate.  If I were to consider one tool over the other, for versatility and pinpoint testing (independent of the PCM/ECU/ECM data stream), the oscilloscope would be my first choice.

    Moses

  12. SomeBuckaroo...Interesting patterns...I would drop the voltage baseline to expose the full height of each spark plug firing spike.  The aim is to compare spike heights and voltage accordingly.  Height is not only about ignition condition, it also reflects relative cylinder compression, a rich or lean burn condition, cylinder fill/vacuum, effects of spark timing and the overall condition of your running engine.  With EFI/MPI (individual port fuel injection), we have the ability to assess and compare the rich/lean burn condition of each cylinder.  This can help clarify how each fuel injector functions.  Carbureted engines did not have that advantage.  We need to read the spark spikes and their voltage heights to make these observations.

    Have you tested or changed your spark plug wires or the coil high tension lead between the coil and center of the distributor cap?  Aside from firing line height, I'm concerned about these ignition components.  The cap and rotor are "good"?  The cap has brass contacts? 

    Run a standard ohms resistance test on the individual spark wire leads (end to end) and the ignition coil high tension lead (spark cable from the coil to the distributor cap).  Twist or coil the wires gently while running these tests...Also run an ohms resistance test on each spark plug (out of the engine and isolated) for comparisons.  Spark plug quality is all over the board these days, even when new.  What kind of spark plugs are you running?  I'm seeing distinct ignition pattern differences between cylinders.

    Moses

  13. Bill W., I am very pleased that you took the time to clarify your fuel mileage, modifications and valuable Ram/Cummins pickup experience...Thanks much!  Below is my reply to your many thoughtful choices and points.  I have red highlighted for an easier read:

    On 2/6/2023 at 10:23 AM, Bill W. said:

    Hello, Mr. Ludel...I am pleased this post is still open for replies and I hope this goes through. I have a few things to share with you about my own experiences with my pickup and my continued quest to get the best mpg I can. I am the second owner of my 2003 Dodge 2500 crew cab SLT 4x4, NV5600 with short bed and HO 305 hp motor. I bought it in 2016 with 110k miles. The first owner took excellent care of it and kept 98% of the receipts, one of the reasons I bought it. Regarding this mpg thread, he did a few mods to it like put on a front leveling kit, Banks Six Gun module, Air Raid cold air box/filter and Toyo 10 ply 295/70-17 tires since he pulled a four horse trailer. My primary reason for buying this Dodge was the excellent condition it was in, the Cummins engine and getting better mileage than my former Ford with a 460 at 10 mpg. The former owner is a wealthy man and when I asked him what kind of mileage he got he didn’t really know. No matter, I drove it from Portland OR to the Bay Area on I-5 and got 19mpg, calculated by hand. I was way happy!

    In hindsight, I would have been happier with the NV5600, its added gear ratios and the control level with a manual transmission, but I do enjoy our truck.  When the four-speed 48RE automatic needs attention and shows telltale wear, I'll likely retrofit an Allison automatic transmission...Your Banks equipment is a step beyond my stock engine with only the Hypertech MaxEnergy software tune.  You obviously bought the right truck with the right history, always a great place to begin.

    Since then I have always been mindful of my driving antics, mostly trying to get the best mileage I could. Reading here, I never considered checking the odo for accuracy but it appears to be correct. The previous owner had the speedo recalibrated to the new tire diameter and it also appears correct. The best mpg I have been able to achieve to date was 23. I too have noticed if my rpm is above 2000 my mpg will go down about the same rate the speedo goes up. Going through Nevada with 70-80 posted limits, my mpg will be 14. If I keep the speed at 65, 2000ish rpm, I will be 19-21, all factors considered. I don’t rely on the lie-o-meter ever other than a trend. I always calculate by hand, every fill up.

    I can appreciate "antics".  One of the only runs where I "pushed" the Cummins was an empty, fast-paced return from Southern California, spinning the engine to 2400 rpm where safe and desolate.  That completed the duty cycle for the OEM water pump, which fortunately waited until I got home to begin leaking in the driveway.  My best pure stock mileage (before installing the chassis lift, oversized tires, the added weight of a cap, a 75-gallon auxiliary fuel tank, massive winch and bumper plus accessories) was 25 mpg on a strictly mileage-oriented trip to Portland, Oregon in the summer of 2011.  I kept the engine in the 1,600-1,700 rpm range and manipulated the throttle like there was a raw egg beneath my foot.

    I have a boost gauge and egt gauge. I monitor them while on grades especially. Previous owner warned me of pulling a grade with a trailer in sixth gear,  not so much for egt but for the trans itself. Just like you, I shift to fifth direct. Researching it, sure enough he was right. An oiling idiosyncrasy inherent in the design. There are fixes for it and I have accomplished them but I still shift down. One thing I noticed in this entire thread is no mention of tire pressure. An easy thing to overlook if one is not a real gearhead but it makes a difference. I have fiddled with this in search of a better ride with 10 ply tires only to the detriment of mpg. Back up to 70psi front and 60psi rear, and mpg returned. New Monroe Magnum 60s in the rear and my bounce was under control. Cheaply too.

    Thanks for drawing attention to the difference that tire pressures can make, very important and grossly overlooked...We're out to preserve the powertrains, we each focus on protecting the transmission.  The transmission is a load limiter on a Gen 3 Ram.  The aluminum case G56 manual transmission seems to fare better (surprisingly) than the rugged, iron NV5600.  I'm probably setting a record for service life from a 48RE automatic in a 2005 Ram 3500.  I did perform a few in-chassis survival upgrades that have helped keep the transmission in service.  The rest of the story is driving technique.  Based on the history of the 46/47/48RE transmissions, the 48RE being the more robust iteration, I'm now past the 185,000 mile mark on a transmission that could have failed during one trip to Moab with our somewhat lighter 8,400 pound travel trailer in tow.  A multiple-horse trailer or hotshot load, misuse of overdrive and high speeds on six percent grades have always spelled disaster with these transmissions...Glad you use direct drive and lower gears on grades. 

    About 2000 miles after getting the truck, the RH unit bearing failed. In an effort to increase mpg, I decided to replace them with free spin hubs. Alas, there was not much of an increase that I could tell. If I were extremely disciplined and had a detailed log before the change to compare to after, it may be more apparent. Being like most drivers, that was not me. There are two redeeming factors though. While backing a trailer I use low range so i don't have to slip the clutch so much and if I have to turn full lock, I don't have the knuckle bump of the u-joints. The second thing is there is a noticeable improvement in braking. Reasoning if the braking is better the mpg would be better and it probably is a small amount. I am still happy I made the change though. Now I can service the bearings. and the hubs can carry more load more evenly. Important for rigs with more positive offset wheels which I don't have.

    The unit hub bearings all fail with time, as do the stock driveline U-joints.  I am now at one pair of new Timken unit hubs.  This spring I'm slated to install SpynTec front wheel hubs with free-wheeling lockout hubs.  (What brand hubs did you choose?)  I'm more concerned about parasitic load and needlessly replacing front axle shaft and driveline U-joints.  I've already done the front driveline and can count on both hands the number of times 4WD had been engaged for any distance.  That's reason enough for the full-floating hub conversion.  Besides, I miss being able to service and adjust wheel bearings like our traditional 4x4 trucks.  Contemporary, quality grease and careful bearing adjustment will increase the time intervals between those services.  

    Using your excellent article/ pictorial on the gear change in your rig, I used it for guidance on replacing my open differential with a Detroit Locker this past July. Thank you, for it as it helped tremendously! I like lockers even if I may suffer a little lower mileage. I have not been able to take a 700 mile or so trip to see if it affected my mpg but my shorter trips like to Tahoe and back are comparable to before. Tire pressure and tire diameter is important with a locker. I’m on it. For what it’s worth, when I bought my rig I sent Dodge my vin to find out if it had a limited slip. I also asked if there was a data plate or sticker/ tag anywhere. Turns out there is a sticker located in the glove box, at least on mine. Check yours. No tag on my diff housing. Incidentally my gear ratio is 3.73.

    My only caution on the Detroit Locker or any other "automatic locker" is when you're on ice, especially an off-camber surface.  If both rear wheels spin simultaneously, the truck's rear can slide sideways toward the low side of the road.  (This is less likely to happen with the Detroit design than with a "factory" multi-plate Spicer Powr-Lok type differential.)  Just be prudent with your throttle application and keep this tendency in mind...I'm a manual locker user, historically ARB, though I'd try an Eaton E-Locker if it were available for the 11.5" axle.  My Ram does have factory limited slip, which has not been an issue.

    Thanks for the comments on the axle ring-and-pinion coverage.  I'm in the process of producing my first "Road and Trail Ready" course for Teachable.com.  The course will be devoted to axle rebuilding and setting up gears.  Prospective students will likely be serious 'DIY' builders and shop technicians.  I'll post the launch date here at the forums.  I like the Teachable.com platform and structure, and my "school" is at https://roadandtrailready.teachable.com. The HD video course will be similar to classroom/shop instructing, which I did for seven years.  Folks may be ready for something beyond YouTube.

    I have read much controversy on this but in my continued quest to improve my mpg, I just bought a S&B intake elbow. This was not a pre planned purchase. Rather an excuse since I was replacing the Banks electrical boost gauge with an Autometer mechanical and I needed a place to plumb the gauge. A very nice piece with metal gaskets, boot, clamp and hardware. Smooth radius and no restriction like the OEM piece, logic says it should help. I did some simple math with a force, area, pressure formula based on the ID in comparison of the two and it calculates favorably. I have just finished this and have not driven anywhere other than down the street so no data yet. I hope to get lower egts while driving and a faster cool down before shutting down at minimum. There may even be a slight increase in boost pressure and sooner spooling with it. To be determined.

    I can't see a downside to the S&B intake.  My only comment is that if we behave ourselves and run the Cummins 5.9L H.O. ISB between 1600-1900 rpm, there's not much demand for improvements or upgrades.  However, your scientific, data based choice is much respected, and I'm sure there are at least incremental gains with this device on an otherwise near stock engine.  Please update us with your findings.

    The last thing I wanted to mention is I was considering going to a little taller tire in order to lower the rpms at speed. 65 is about as fast as I can go and stay below 2000rpm. The boost gauge is about 10 at that speed. I’ll have to double check. The Toyo tires on it are about 33” I was thinking about a 34-35” tire. I have not done the math for rpm yet but wanted to quiz you again that you thought your own motor was under too much load and therefore required more boost to overcome drag and load? If I could get a comfortable rpm below 2000 at 70 I think I would be happy. I read on another post on  your site that another fellow , Steve Atkins, changed to 3.54 gear ratio and had a dramatic  improvement with a second gen. I'm not going to change ratios, just tire diameter. Looking fwd to your reply.

    This is a bit dicey.  I briefly ran 35" (actually 34.6") oversized tires with the OEM 3.73 gears and my 31-percent overdrive.  Fuel efficiency actually went downsubstantially.  I then had the necessary choice of 4.10 or 4.56 axle gears and chose the latter.  My aim was to not put an excessive load on the 48RE with its wide split between 3rd (direct) and 4th (overdrive).  I rationalized that the 4.56 gears also would be best for legal speed trailer toting (55-65 mph).  After the installation came the realization that our primary mileage is on I-80 without a load.  2000-up rpm is the end of optimal fuel mileage.  (I appreciate your reference to 14 mpg at speed.)  To drop rpm, I went to 37" (actually 36.5") diameter tires, making it even more difficult for my wife and passengers to enter the cab.  (This also pressed the 4" chassis lift to extremes and marginalized the tires-to-front wheel tubs clearance.)  Your plan for 35" tires would necessitate a chassis lift, 4-inches being sensible if you do go this route.  That's a significant undertaking.

    The lift opens Pandora's Box.  When I brought up fuel mileage with my friend Jim Frens (former executive platform engineer at Chrysler for both Jeep® and Ram trucks), he smiled.  I shared my willingness to install an Eaton medium-duty truck 7-speed manual transmission to eliminate the stigma around gear ratios.  I have always enjoyed welding and metal fabrication, beginning as a light and medium duty truck fleet mechanic then later as an instructor at Welding and Automotive Technology.  The steps for converting to a heavy seven-speed medium duty truck transmission did not deter me, though my wife of 46 years did raise her eyebrows.  Jim leveled with me, stating the obvious:  Our trucks have terrible aerodynamics.  The faster you go, the more these physics challenge your fuel mileage.  Add the load and friction coefficients, it gets even worse.  Notably, our Rams with a taller trailer in tow are akin to pushing a billboard down the road.  Jim qualified this in practical engineering terms.  Yes, gearing and overdriving tire sizes matter.  However, more importantly for fuel efficiency, Jim suggests slowing down.  We know that works. 

    My target for the Cummins engine remains 1600-1900 rpm at reasonable cruise speeds.   To bring the truck closer to factory dynamics (short of restoring the vehicle height and eliminating the huge Warn winch bumper), I have 35-inch diameter tires on hand and am considering 4.10 gears.  I'd like to go 69-72 mph on I-80 without feeling pain at the pump.  I may do the gearing change in conjunction with the full-floating front wheel hubs installation.  My wife would appreciate the improved ingress and egress when entering and exiting the cab.

    Please keep us informed, Bill.  Your experiences are valuable and well tested!

    Moses

    Thanks again for ALL of your work and publications!

    Bill W.

     

  14. SomeBuckaroo...Pleased you're working with the oscilloscope!  Glad you clarified, I was about to answer your original comments referring to the photos, and the additional information is helpful...The offset "correlation" could be due to a simple factor:  the spark plug firing lines reflect spark in timing advance mode while your MAP probe or indexing channel could be picking up either the voltage (+) or ground (-) from either the camshaft or crankshaft position sensor

    2000-up Coil-On-Plug engines actually share the 5V (+) camshaft position sensor lead with the MAP sensor.  The '98 wiring system may be picking up a similar reference or at least feedback.  As a D.C. system, completing the ground or reading the positive supply voltage will show as an "open" unless the +/- circuit is complete.  While your PWM/hysteretic theory is certainly a consideration, it's not likely at play here.  (A voltage reading of that sort would not be a consistent, repeated single spike with uniform height.)  The MAP line is consistent and appears at the same timed interval with uniform voltage.  It also is in relative sync with the #1 cylinder firing line.

    To verify what I'm suggesting, confirm that the MAP voltage line is consistently just a few degrees from the spark firing line for #1 cylinder.  This would reflect the normal spark timing advance with the engine at idle.  You can even verify the amount/degrees with your timing light:  break down the offset degrees in your scope lines, they should match with the number of degrees of spark timing advance seen with the timing light.

    The crankshaft position sensor indicates a true and constant TDC for #1 cylinder, as this signal comes from the flywheel.  Unless the camshaft is painstakingly "degree'd" during engine assembly, the camshaft position will deviate slightly ("retarded") due to timing chain slack/wear.  A camshaft position sensor signal in a distributor engine like yours will also reflect the distributor drive gear wear.  The camshaft position sensor is monitoring the degrees of valve timing error between the crankshaft and the camshaft.

    When the cylinders' spark firing lines parade with the engine running, these firing lines are X-degrees of advance from TDC.  You can alter the engine speed to get a shift in spark timing advance (confirmed with your timing light) then see whether that shows up on the scope as the number of degrees of separation between the MAP probe line and the #1 cylinder's spark firing line.  This will test the theory...Keep in mind that the camshaft position is 1/2 the crankshaft degrees, so this could even break down whether the MAP channel probe is picking up the crank position sensor signal or the camshaft position signal.  Your timing light reads crankshaft degrees while the camshaft position sensor is picking up camshaft degrees.  The crankshaft rotates twice (720 degrees) for each 360-degree rotation of the camshaft.

    To your point, if this theory has the MAP channel reflecting the crankshaft or camshaft position as opposed to the #1 spark firing position, the spark line adjacent to the MAP probe spike is number one cylinder firing.  If the parade is reading correctly, you can move to the right to pick up the other cylinders in the 1-5-3-6-2-4 firing order.  To confirm, remove a spark plug lead (with either insulated spark lead pliers or the engine shut off!) and see whether that cylinder drops out of the firing sequence.

    I see some firing symptoms worth discussing.  Before doing so, if it's possible to flip your voltage spikes to the upside instead of facing downward on the scope, I can share what the firing lines represent.  I'd like to see an image of the six cylinders in parade plus a stretched view to a clear single cylinder (#1 cylinder, preferably).  I'll explain what you're seeing.  Despite modern ignitions and PCM spark timing management, the firing line and other features are similar to scope patterns we read on breaker point ignition systems over fifty years ago.

    Moses

  15. Nash...If gas is "flooding" over from the float bowl, the carburetor's needle/seat and float level need attention.  The float could be dropping too low and cocking the needle open.  The float level could be set too high.

    If gasoline is coming up from the throat of the carburetor, that's an internal circuit, gasket or check ball issue.  If you have not changed the ignition timing, this should not be "backfire" flooding.

    Was the carburetor used?  If so, I would bench strip it and carefully follow the instructions that come with a rebuild/overhaul kit.  Make sure all parts are in place and match up properly.  Is this carburetor a genuine Carter AFB, or is it a similar Edelbrock four-barrel?  If a true AFB, what was the engine application for this carburetor? 

    Moses

  16. Jon73...This sticker is a clue.  My references to "all" Jeep CJs have a catalytic converter was based on a 1979 Jeep FSM.  1976-up California models had mandatory catalyst systems.  Information from reliable owner references share that their 1976-up official FSMs have the same quote as my '79 manual:  mandatory catalytic converters.  Yet some owners share that their Jeep CJ has a NON-CATALYST decal like you found on a 1976, 1977, 1978 or 1979 model. 

    California vehicles were all equipped with a cat from 1976-up, but Federal (EPA requirements only) may have allowed NON-CATALYST vehicles.  Your Jeep CJ-7 is Federal-only (49-State) and may be among a group of legally NON-CATALYST vehicles as the decal suggests.  If that's the case, the EPA could have allowed AMC/Jeep a gradual phase-in of cats on CJs.  These were lower production volume "light utility trucks" for emissions purposes.  California had its own standard, and beginning in 1976, required both EPA equipment and in many instances additional devices.

    You may be off the hook on the cat requirement.  A California smog station should be able to determine this.  A pre-test or just a visit to a smog station would be helpful.  If this doesn't get answers, visit a BAR "referee station".  They can reach a VIN or other determination around vehicles that were exempted from the cat requirement.  This would likely apply to 49-State vehicles like yours.  If there is proof that a U.S. EPA vehicle (not an imported "grey market" vehicle) did not require a cat when new, you should not have to install one to meet California smog requirements.  There must be verification that the vehicle is NON-CATALYST, which your CJ's aging decal notes.  If so, you will not find evidence of a California emissions sticker under the hood, just the EPA sticker.

    As a footnote, California smog law would not allow a 49-State vehicle to register at California until the vehicle met either a time or minimum mileage requirement.  This was intended to prevent consumers from buying a 49-State vehicle in an effort to "defeat" California smog requirements.  Vehicles brought into the state after the time/mileage period could be smogged and registered without adding equipment.  Your Jeep is light years past this requirement threshold...Jeep CJ emissions and engine equipment became uniform from 1981-up.

    Let us know what you turn up at the smog or referee station...

    Moses

      

  17. Jon73...You picked a good model year and chassis...A straightforward overview of California requirements for your Jeep and other vehicles is at https://www.bar.ca.gov/consumer/smog-check-program/faq.  You will be required to "smog check" the Jeep for registration.  The FAQ talks about the pre-test that is available, which would determine which parts are either missing or needed.  Beyond this, see my comments below (red highlighted):

    11 hours ago, jon73 said:

    I bought a 1978 CJ7 out of Arizona and brought it to California.  Before I go through the process of registering it, I'd like to understand what I need to do for emissions and what it might cost.  The Jeep has changed hands many times, so I don't know where it started life.  I believe it has the original motor and transmission.  Vin decoder matches.  258 single barrel carb and 3 speed transmission.

    Arizona does have smog requirements, though I'm not clear what model years are no longer required to smog.  For California, 1976-up model years still must test and pass smog.  

    Two significant identifiers would be the VIN (your research) and the decal(s) under the hood.  If the decals are original and not deleted, an EPA-only decal (without a California decal) indicates a 49-State vehicle.  If your Jeep is a "Federal" (EPA) emissions 49-State model, you will only be required to restore its original equipment.

    There was originally a catalytic converter and unleaded fuel restrictor in the fuel filler tube on all six-cylinder 1978 Jeep CJs.  In 1979, California models used a monolithic and a pellet catalytic converter.  (The monolithic cat is a part of the exhaust head pipe.)  Your vehicle may have been "49-State" or "50-State", so look for the head pipe monolithic cat and other features.

    The air pump sounds like the AMC "Air Guard" system that feeds through a diverter valve and into the exhaust manifold via tubes.  You need the diverter valve, hoses, tubes and the air pump...Equipment that came on your 1978 Jeep CJ-7 with a 258 inline six—either Federal version or Federal-plus-California, is similar.  There should be an EGR system on either system routed through a coolant temperature vacuum switch (CTO).

    The engine has a smog pump and exhaust manifold collectors.  It does not have a CAT or O2 sensor in the exhaust system.  Some dangling wires but not all hacked up.

    Your vehicle is in the cat era but not yet an electronic "feedback" carburetor and ignition (typically 1981-up for Jeep) that required an O2 sensor. You would not have an O2 sensor in 1978...You do need the Thermal Air Cleaner (TAC) in place and functional.  There was an elaborate carburetor device for cooling the float bowl after shut-down.  (This may not have plagued your 1978 model.) 

    Most emissions tests on older vehicles fail the visual inspection for items like the air cleaner or even simple things like the foil tube to the exhaust manifold, a non-functional exhaust heat riser or a missing EVAP canister

    A California smog station will go over your vehicle with a list of items that must be in place and functioning, including the evaporative emissions system components and the fuel tank EVAP hoses.  A bad/non-sealing gas cap can fail an emissions test.  Engine vacuum hoses and thermal vacuum switches are other red flags.  You also need a properly routed PCV system (closed crankcase).

    The choke must be original (not an aftermarket hand choke kit) and functional.  This is a concern for both the visual inspection and practical side of a tailpipe test for CO, HC and NOx.  A choke partially closed will not meet tailpipe emissions. 

    While this all sounds dire, it's mainly the visual inspection that counts.  The engine in good operating condition, tuned properly and with all original emissions hardware intact will pass the tailpipe emissions test levels for an older vehicle.  California does not expect your vehicle to meet its OEM emissions levels when new.  There is an allowance for vehicles as they age.

    I've looked on line, but unable to find a full layout of what I need.  Wiring diagrams don't show O2 sensors, so maybe that's not required.  I have found evap canister routing and mapping.

    Yep, you will need to get the EVAP system to pass both the visual inspection and a vacuum test.  If the canister is clogged or defective, a new or good used one will be required.  You won't need an 02 sensor even if a catalytic converter is required.  A 1978 CJ Jeep has no "computer" or engine sensor/control module.  There is a "timer" on the carburetor bowl cooler.  It's questionable whether a vehicle would fail for not having the cooler operational.

    If its a emission 49 vehicle, will I need to meet California standards or can my vehicle be stock to where it was sold?

    You are not expected to convert a 1978 49-State vehicle into a 1978 50-State vehicle.  If 49-State, it must have OEM emissions equipment in place and pass the tailpipe test.  There are referee stations and other California remedies available when parts to restore a vehicle's emission system are no longer available.  These involve going through the BAR smog program.

    The ignition distributor must be stock type or an approved (California E.O. number) aftermarket type.  If the distributor has been changed to aftermarket, it must have a California E.O. number to pass emissions.  The spark advance must function properly, and base timing must be set to the degrees noted on the underhood emissions decal or in the FSM.  The carburetor must be set to stock idle mixture (lean drop) and idle rpm.  These are basic tune related settings that must match OEM settings to pass the test.

    First determine whether this is a 49-State vehicle or a 50-State vehicle.  We can break down the specific equipment needed from there.  I have a '79 Jeep CJ factory shop manual that should detail most of what you need to restore the system.  My parts catalogs go back to 1981, which won't help a lot, though there are some 1980 carryover pieces.  (Export model parts would include emissions exempt vehicles that may have parts resembling earlier Jeep model years.)  The major change years for emissions were 1980 to 1981.  1981-up CJ 258s have the BBD carburetor with Sole-Vac feedback and an electronic ignition with sensor feedback and a control module. 

    Let us know what you find in decals and other fine points.  Check the air pump system to see whether there is a line/hoses to a diverter valve.  The closer the Jeep is to stock and unmodified, the better off you will be.  The California emissions inspection process is two-fold:  first visually checking for engine and chassis related components then finishing with a tailpipe emissions test.

    It may pay to get a pre-test and visual inspection.  There could be exemptions for certain missing equipment that is considered obsolete or that does not "defeat" the smog system.  A catalytic converter, EGR or air injection system will likely need to be in place.

    Moses

    Thanks,  Jon

     

  18. Jeepdog...Go through my list of concerns (last reply), including the unobstructed return flow of fuel from the fuel filter to the tank.  (This helps prevent excessive pressure from unseating the carburetor's float needle.)  If fuel pressure is unclear, check the fuel pump pressure and volume on the line going into the fuel filter.  Instructions are in the factory service or shop manual (FSM).  

    Check for vacuum leaks as I suggest, including the WD-40 tests...Underhood and chassis vacuum hose diagrams are in the FSM.  Are you using an FSM for your Jeep model? 

    Moses

  19. Jason...I looked through all of my Toyota service books from your era.  Anything mechanical, service related specifications or shop procedures are in my Toyota service manual archives.  Sometimes the factory owner's manual (glovebox book) has these details, but Toyota did not include that information in handbooks from your era.  The jack stowage point is not shown.

    This information would be body related parts.  A Toyota dealership parts illustration or schematic drawing should have the details you need, including the mud flap mounting method.  3rd Generation 1979-83 parts should be similar.  If your local Toyota dealership's parts department has coverage that far back, you should find answers.

    As I recall, there is a metal strap plate that holds the jack to the floorboard behind the seat.  That strap plate may be included in your tool kit, it would be flat with a hump for the jack handle.  Again, dealership parts personnel should have precise answers.  Perhaps a forum member can add information here and even some photos.

    Whenever I work on or restore a vehicle, my first step is to find a factory shop/service manual and, if possible, a factory parts catalog with schematic drawings.  eBay can be a good source for these books, though availability is a matter of timing.  My preference is first generation factory books.  Bentley Publishers (my book publisher) did produce an in-depth service manual that offered considerable material.  That book was done by Bentley staff in-house and is the Toyota Pickup & 4Runner Service Manual 1978-87.  I have a copy, but like the Toyota FSMs, there is no mention of the jack stowage method or location.  I did not provide these details in my Toyota Truck & Land Cruiser Owner's Bible™, either.

    Regarding all things mechanical, I've got your back.  Does your truck have a 4- or 5-speed transmission?  The early 4x4 5-speeds had issues with the transmission's input gear bearing.  There were warranty upgrade/supercede bearings available in the mid-eighties, and eventually these transmissions received a larger input bearing.  4x4s and diesel powered models experienced the bearing failure.

    Moses

  20. SomeBuckaroo...You're welcome...I like your approach...Since you have a distributor ignition, I would do the scope test you describe with the capacitive probe placed at each cylinder in the firing sequence:  1-5-3-6-2-4.  See if that shows distinctions.  #6 is opposite #1 in firing sequence, and even those two probe points would be handy.  Assuming the ignition spark wires, cap and rotor are in top shape, spark firing patterns would be revealing and provide the comparison you need to isolate given cylinder(s) weaknesses.  A reading like this (spark firing lines) would come from the high tension coil lead if your scope can catch this.  

    You'll need to experiment with you real time MAP readings.  You're right, vacuum to the MAP would likely reflect averages rather than pinpoint a given cylinder's vacuum pulses.  We're working with milliseconds here.  My Autel MP408 oscilloscope and a back probe might read the MAP sensor's electrical/electronic signal to the PCM as a fluctuating voltage reading.  Here, however, the MAP sensor has converted the engine's vacuum signal into a quantity of voltage, much like a potentiometer. 

    What would work, though, is my 4-channel MP408 MaxiScope plus the automotive pressure/vacuum pulse sensor that I picked up for under $75 at eBay from a British Columbia manufacturer. The pulse sensor probe (hose) can be placed in the tailpipe.  Exhaust pressure pulse readings reflect fluctuations or losses of pressure in discernable milliseconds. 

    When we hook up the MaxiScope with a channel/probe to reference #1 cylinder, with another channel/probe showing all six spark firing lines, we can pinpoint pressure losses at each cylinder with the engine running.  The pressure pulse and other reference signals would show precisely which cylinder(s) have a drop in pressure.  This is why I get excited about the oscilloscope.  The MP408 and OAK (optional accessories kit) have become my go to diagnostics tools for mechanical and electrical testing of anything that produces voltage over time.  I don't minimize the value of a scan tool, it can be a great device for peering at PCM data in real time or tracking signals to and from a PCM/ECU/ECM.

    Here is how I would use the OTC 5609 leakdown tester.  Tests are done with all spark plugs removed: 

    1)  Tune-up related diagnostics—First-off you want comparisons of the leakdown rate/percentage per cylinder.  This is cylinder "balance" and a great tune-related test.  Since the leakdown test has the engine/piston static at TDC on the compression stroke, the valves are seated as well as they can be.  (Run the test with the piston at TDC on the compression stroke as intended.  This has the piston at the maximum cylinder taper point for leakage.)  If valves are closed when applying tester pressure, there is less risk of debris blowing between the valve face and seat, which would cause a false reading.  On an older engine with carbon buildup around the valves, this is a precaution when running the leakdown test.  You're blowing compressed air into the cylinder through the spark plug hole.

    2)  Pinpointing piston ring and piston issues—Think of this like a standard compression test only much more precise.  With the air pressure applied, leakage past the rings or a worn/damaged piston will create a distinct air flow noise in the crankcase.  This can be heard by ear or with a stethoscope at the dipstick tube—or simply by removing the oil filler cap.  Compressed air goes into the cylinder, a percentage of it blows past the piston rings (i.e. the term "blow-by") and enters the crankcase.  You can hear the air movement.

    3)  Pinpointing valve seepage—Again, although you don't have the running engine to rock the valves (weak valve springs or uneven seat/valve face relationship could be more pronounced with a running engine and firing loads), you have the optimal vantage for pinpointing valve seat and face pitting, uneven seat cuts or warped valves.  The compressed air is leaking past the intake and/or the exhaust valves.  If leaking past the intake valve, you will hear the air exiting from the throttle body throat (open the throttle for a clearer read) or air cleaner box.  If leaking past the exhaust valve, you will hear noise at the tailpipe, either by ear, with a stethoscope or using a sounding tube.

    4)  Blown head gasket or casting crack and warpage—A blown or seeping head gasket will also turn up.  Remove the radiator cap and look for bubbles with the leakdown tester applying pressure.  (If you suspect a blown or seeping head gasket, remove the radiator cap before running the leakdown test.  You might otherwise damage the radiator from the air pressure.  Set the leakdown tester's pressure low.)  If there is a valve seat crack, cylinder wall crack or blown head gasket, bubbles will appear in the radiator.  If a casting crack is lower in the cylinder, lower the piston enough to expose the crack but not open a valve.

    Note:  Like with a compression gauge check, a blown head gasket may be between two cylinders.  Listen at the adjacent cylinder's spark plug hole while performing the leak test.  The leakdown test is an audible test for flowing air. 

    Since you could have a combination of leak points (rings, intake valve or exhaust valve), you may identify air flowing at several points.  Distinguish the noise sources and volume.  If just ring seepage is suspected, you can try the traditional use of a few squirts of clean motor oil into the cylinder then run the test again.  There should be at least a brief point where the leakage/percentage decreases significantly.  Always make sure you are at TDC on the compression stroke to be sure that both valves are seated.

    Valves seal thoroughly and should not leak air.  However, conventional automotive rings have end gaps.  With end gaps, there will always be a certain amount of air seepage past the rings, which is normal.  This establishes the baseline percentages for "normal leakage".  8-10 percent leak is excellent for a production engine in new or "broken-in" state.  12-percent is still tops for modern engines with high compression ratios. 

    I consider an engine in "good operating condition" to as high as 20-percent leak as long as the percentages between the highest and lowest cylinder are not far apart.  Higher percentages reflect general wear, but at 20-percent leak, the engine may still have balanced, acceptable performance.  Beyond this, the engine is declining, may be using oil or should be considered "worn" to the point that a tune-up may not make much difference.

    The value of a leakdown tester is its ability to diagnose current and pending troubles.  Here is a test that shows valves building carbon or starting to seep between the faces and seats.  Or rings that are losing seal but are still "functional" for now.  I use my leakdown tester to gauge the approximate cylinder taper...Lower the piston in the cylinder without opening a valve.  As the piston moves down, the cylinder wall taper decreases.  If the percentage of ring blow-by/leakage decreases with the piston lower in the cylinder, there is a likelihood of cylinder taper or upper cylinder scratches.  I have a bore scope to look closely at the upper cylinder walls and taper area.

    A leakdown tester can even measure valve chain/belt wear, camshaft lobe wear or valve opening events (valve timing).  With a degree wheel on the crankshaft and the tester applying air at TDC on the compression stroke, slowly rotate the crankshaft in its normal direction of rotation to where the cylinder's exhaust valve just unseats and begins to "leak".  Do not pass this point and rotate the crankshaft backward to compensate.  Rotate the crankshaft in one direction.

    Note the degree on the timing wheel where the exhaust valve begins opening.  Compute valve timing from there.  (This is not the usual 0.050" ramp camshaft lobe/lifter height test.  Therefore, these results will not match the camshaft manufacturer's advertised specifications.)  Based on the camshaft profile, the intake valve timing can be computed from here.  This would be a test for wear and damage in the valvetrain.

    The leakdown tester enables testing a static engine in a vehicle, laying on the shop floor, chained to a cherry picker (near the floor or with a safety stand supporting the engine), resting in a pickup bed, at a recycling yard or on an engine stand—anywhere compressed air is available.  Your leakdown tester can be used for checking the cylinder seal of any I.C. gasoline engine, from a freshly built automotive long block to a high mileage used engine, from lawn mower engines to motorcycle, passenger car or truck engines.

    After running the leak test, as a follow-up, you can use an inexpensive bore scope to inspect for carbon buildup, cylinder wall damage or signs of casting cracks.  Creative thinking will open up even more uses for the leakdown tester.  This is a quick way to understand engine dynamics and an engine's overall mechanical condition with the cylinder head in place.  In addition to the leakdown tests, you can consider:  1) the engine's oil pressure and bearing condition, 2) the precise valve lift and 3) the valve timing.  Then you have the whole picture.  

    Let us know what you find...

    Moses   

      

     

  21. Jeepdog...Glad to help, you have a really clean Jeep and great looking engine.  The engine needs to run right.

    The idle with needles turned in all the way is a distinct clue.  Either the carburetor is flowing excess fuel or the engine is getting fuel from somewhere.  Closing the needles cuts off fuel flow through the carburetor passageways.  If the idle is unaffected, there is another source of fuel sustaining the rpm—or there is a vacuum leak either at the base of the carburetor, the intake manifold gasket or at a vacuum pipe/hose to the carburetor.  

    Using WD-40 or an equivalent low volatility spray, spray a light mist around the carburetor base with the engine idling.  Listen for engine speed changes that indicate a leak.  Check other vacuum hoses that might allow air to enter the intake stream.  Avoiding hot areas while spraying a light mist, spray at the intake manifold junction with the cylinder head.  If speed changes, the intake manifold gasket is leaking.  Check around the vacuum switches, too.

    You have the idle step-up solenoid for when the air conditioner is running.  When adjusting the idle mix, is the engine rpm (speed stop) low enough to attain a normal idle speed?  Is the step-up solenoid preventing the idle speed adjustment from dropping to normal?  The idle rpm speed should be on the tuning/emissions decal.  If not, see the 1984 Jeep CJ FSM details below:

    BBD Idle Speed 1984 Jeep CJ 258.jpg

    BBD Idle Mixture Drop 1984 Jeep CJ 258.jpg

    BBD Specifications 1984 Jeep CJ 258.jpg

    Another concern I have is the return flow from the fuel filter to the tank.  This must be unrestricted.  Your fuel lines from the tank to the filter, from the filter to the carburetor and from the filter back to the fuel tank must be routed correctly.  The third pipe on the filter (return to tank) serves two purposes:  1) helps prevent vapor lock by continuously moving fuel through the system and 2) importantly, to prevent too much fuel pressure from unseating the carburetor's float needle.  If these lines/hoses are not routed correctly, excess fuel pump pressure can unseat the needle, raise fuel level in the bowl, and cause a flooding or overrich condition.  Also, the air vent hose above the carburetor's float bowl must be routed correctly.  Otherwise, the bowl is pressurized, which could unseat the float needle or force fuel through the carburetor. 

    Note: The emission vapor canister is part of this system and its hoses must be routed correctly.  Make sure the EVAP hoses and the canister's vacuum source are correct.  Make sure hoses to the fuel tank and filler tube are routed correctly and unrestricted.  Roll-over valve(s) at the tank (if so equipped) must function normally.  Fuel tank pressure must be normal. Be sure the EVAP system is not restricted or malfunctioning.

    A fuel pump with too much volume or pressure output can unseat the needle, too.  I see a mechanical fuel pump.  If necessary, check the fuel pump output pressure and compare to the OEM recommended pressure. 

    Another concern is the EGR system.  EGR and the ignition spark advance are each applied with carburetor ported vacuum, not manifold vacuum.  They are both regulated by the TVS (thermal vacuum switch), which prevents EGR function and ignition vacuum advance until the engine warms.  The TVS threads into an engine coolant port (typically at the cylinder head or thermostat housing).  Around 140 degrees F, the TVS (wax pellet valve) opens and allows the ignition (vacuum) spark advance and EGR valve to operate.

    If the EGR valve is attached to manifold vacuum, you will have a constant rich condition.  Unspent/unburned hydrocarbons and other emissions in the exhaust will constantly recirculate through the intake stream.  This could soot up the spark plugs.  Since carburetor ported vacuum normally applies the EGR valve, the EGR should only operate off-idle (not during idle) then tapers off as the engine speed/throttle increases.  Just like vacuum spark advance, the EGR opens under maximum (carburetor ported) vacuum at throttle tip-in and operates through approximately the first 1/4 or so throttle opening.  Check the vacuum hose routing to the EGR valve.  This should be carburetor ported vacuum supply.

    As for coolant circulation through the intake manifold passage, the simple test is whether the inlet and outlet manifold coolant hoses have nearly equal temperature.  This can be confirmed with an inexpensive ("Harbor Freight") non-contact infrared thermometer.  You can confirm actual manifold temperature with the infrared thermometer.  As a footnote, your heater would not be working if this coolant passage were clogged.  

    Check out the points of concern here, beginning with the EGR, which can cause real havoc if the EGR valve is either stuck open (frozen piston) or receiving constant vacuum.  This would hold the EGR valve open at all engine speeds and throttle openings.

    Let us know your findings...

    Moses

     

  22. SomeBuckaroo...Thanks, and have a productive 2023! 

    As for the vacuum test, there's something amiss.  An MPI engine should have uniform vacuum.  You're showing a rhythmic fluctuation, not extreme, but related to the engine's firing order.  This could be valve seating issues from either your valve spring concern or poor valve face-to-seat sealing at one or more cylinders.  The short block's cylinder seal (basically the piston rings) should be uniform, which you can confirm with a precise leakdown test.  If so, the fluctuation would be a valve(s) and its relationship to cylinder seal with the engine running.

    Your reman short engine is textbook for a 4.0L core in reasonable condition.  This is the typical "reman kit" sizes that shops order for good cores.  You have a thorough rework of a short engine/core on its first rebuild.  A production reman shop would recondition the rods, deck the block, usually line bore the mains, replace cam bearings and freeze plugs and fit pistons during the final honing of the cylinders.  Some shops include balancing, most charge extra for this service or build the cost into the package price.  An inline six will benefit from balancing, though this is not as crucial as it would be for a 90-degree V6 engine without a counter-balance shaft.

    Head work would require a conversation with the shop to determine their "standard" head rebuild.  (At this stage, you may not want to bother.)  The charge is not high, which does suggest that the original valves and springs were reused.  The machining likely included surfacing the head, seat work and valve refacing.  If that's the case, correcting the pushrod lengths would be necessary due to the block decking and head surfacing.  The cost left little or no room for replacement valve seats or new exhaust valves, which many shops replace routinely.  As I've shared, reman shops usually replace all valves, which they buy in bulk at discounts.  This saves labor time.  New valves also help eliminate valve stem height and spring pressure issues.

    Fuel trim looks reasonable, not indicating an issue with fuel flow or mixture.  However, I would do a routine intake manifold and gasket leak test—leaks can cause manifold vacuum fluctuations.  Use a lower volatility spray like WD-40, and with the engine idling, spray around the intake manifold flanges at their cylinder head junction.  (Avoid spraying on the hot exhaust manifold!)  Listen for rpm changes.  This would indicate seepage of air into the intake stream, which affects A/F ratio but also causes variations in manifold vacuum.

    Vacuum hose or brake booster leaks can cause fluctuations, too.  Check the brake booster's check valve (an inexpensive item) and its grommet for leaks.  A clogged cat or muffler can create fluctuations.  Bent pushrods, too...Rule these out as well.

    This is a process of elimination...

    Moses  

  23. Jeepdog...Regarding the spark plug with a clean outer porcelain and rich mix near the ground strap, if each plug looks like this, it could be the MSD ignition burning the fuel mixture in this manner.  If each plug looks like this, the pattern would have to be firing/spark related.  (It's highly unlikely that every plug would line up or "index" at the same position in its combustion chamber, which rules out intake flow anomalies.)  Due to the lower float level, you still have a rich air/fuel mixture just with less available fuel.  The combustion mixture still appears rich.

    If the tag is valid for your carburetor, it was built March 9, 1984.  The number "4" on the tag is for the year, in this case 1984.  My 1984 Jeep CJ factory workshop manual shows two BBD carburetors:  8383 and 8384.  Main metering jet numbers are 120-392 for each of these carburetors.  Main jet size is 0.092".  Metering rod numbers are 75-2384 for both OEM carburetors.  I have other detailed specifications for these two CEC/feedback carburetors that are your engine's era. 

    The number on your tag is lower than Jeep CJ 1984 applications but much higher than 1974 AMC tag numbers.  Why are there no Sole-Vac or feedback features?  What was the listed model application for this carburetor when they sold it?  Both four- and six-cylinder engines had computer controlled (CEC feedback) systems from 1982-84.  CJ 258s were Computer Emission Control from 1982-86 with 1987-90 YJ Wrangler 4.2L/258s also having this system. 

    I went to eBay, and there is a bumper crop of carburetors for these model years without CEC features like Sole-Vac or feedback systems.  Are these hybrid carburetors?  Off-shore knockoffs of the BBD?  They have no provision for a CEC system.

    Your carburetor looks like a genuine BBD.  There were 258 sixes in Eagle cars and J-trucks in 1984.  I-H used the 258 AMC sixes but went out of the light truck business after the 1980 Scout II.  I can look further for the actual application of the 8128S carburetor if that would be useful.  We could determine where that tag originated.

    A few other factors to consider:  1)  Is there sufficient heat below the intake manifold while the engine is warming?  2)  Do you have a thermal air cleaner installed for the warm-up period?  2)  Are the venturi and other pieces original to this carburetor?  The main jets seem correct.  Are the metering rods right?

    Moses

  24. A very neat, clean and pristine installation!  Years ago, I had a 1955 Ford F100 pickup that was a testbed for engine and transmission swaps.  I made mounts that fit to the factory engine and transmission mounting positions.  This required virtually no modifications other than a few drilled holes.  I eventually did restore that truck to a near stock condition.

    At the time, these now classic '53-'56 Ford F100 pickups were plentiful and popular for "hot rodding"—often brutishly modified.  I can appreciate your concern for authenticity and option to restore your valued 1982 Toyota Hilux 4x4 to its original form. 

    You have a classic truck.  The early 4x4 Toyota compact pickups with a beam front axle featured the indestructible "300,000 Mile Club" 22R engine.  I had three FJ40 Land Cruisers:  1971, 1976 and 1978.  The latter two were extensively modified OFF-ROAD Magazine project vehicles, the '76 in the late eighties then the '78 in the mid-nineties.  The '78 was a floor feature at the SEMA Show, Las Vegas...Toyota had it going on!  Enjoy your truck.

    Moses

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