Moses Ludel

Well, we've each become expert at "delayed gratification". I purchased the Honda XR650R on September 30, 2013 and finally registered it for road use (including the road test) at the end of April 2014! Lots of delays, including the sublet machine work, addition tuning, restoration of the dual-sport conversion package, the usual "parts on order" through my preferred local dealership (Big Valley Honda at Reno, Nevada), then the entire filming process... Break-in is critical to engine longevity and a reliable outcome from any engine rebuild. In response to your question, I've begun a new topic to clarify my break-in approach...Trust you'll be on the road soon with the KLR, Forman! Moses

You're welcome, Alberto...The fuel/carburetor, emissions system and ECU is so interconnected that the whole system must be restored in order to function properly. This will take time and careful evaluation. It's unfortunate that previous owners and some mechanics believe that it is useful to "disconnect" and discard various components. In tampering like this, the function of the entire system suffers. "Restoration" seems the only real fix with this complex stock system—or an EFI conversion like the Howell Engineering TBI package if you can afford it. (Click on the link for details.) As for the diff cover sealing, silicone RTV works well. Use a type recommended for exposure to gear lube. Do not overcoat, apply a uniform bead that will smooth out evenly and seal properly. (3/32" to 1/8" bead size is plenty.) Make sure the diff cover is flat around the bolt holes, and torque the bolts snugly to specification and evenly. Do not over torque the bolts, or you will indent the cover at the bolt holes and risk a leak. Snug all bolts to just seat the cover, then let the RTV set up slightly before tightening bolts to final torque. There is no need for a gasket if you do this properly; in fact, average quality cut paper gaskets are more prone to leaking than silicone RTV alone. The later factory use of RTV instead of a cut gasket suggests that RTV works better. (An exception would be rubber gaskets like those found on the Ram truck's AAM axles. These work very well.) I use RTV for Jeep diff covers. Keep us posted, Alberto, enjoy your Wrangler and be safe in your travels! Moses

Welcome to the forums, Alberto! Your photos are very helpful, and so is your description of the problems...Here are some observations: 1) The floor getting hot and the high altitude lack of performance are related to the catalytic converter and exhaust system. This engine uses a Pulse Air catalytic converter, and the air tube from the exhaust head pipe to the catalytic converter has been eliminated. This prevents complete burn in the catalytic converter and also eliminates the pulse air system's cooling effect at the converter. (Lack of a Pulse Air hookup would fail a U.S. emissions test.) In your case, the catalytic converter, if still intact, is either not functioning properly or is likely getting extremely hot from a rich fuel mixture and the missing Pulse Air function. (Tip: The Pulse Air catalytic converter should have an air inlet pipe that works with the pulse tube system.) 2) You have valid concern about the exhaust heat and the plastic fuel tank. In many cases, the heat you describe melts the fuel tank. In a worst case scenario, this could cause fuel to leak onto a super hot exhaust pipe and either set the vehicle on fire or cause the tank to explode. From the tailpipe's "rich" burn signs (black and sooty at the exit), plus your poor fuel mileage, it's quite possible that the carburetor is running way too rich. This could be either a carburetor issue or the wide open throttle/limp mode may be operating all the time due to a wiring or vacuum circuit defect or tampering. 3) Click on this link for the detailed 4.2L BBD carburetor rebuild articles at the magazine. The BBD carburetor requires careful attention to detail during a rebuild, Alberto. You will also find a number of articles related to 4.2L engine tune and troubleshooting at the Search box keyword "BBD". To save you time, here is a link to the lengthy list at the magazine: http://www.4wdmechanix.com/4WDmechanix-search-results.php 4) The previous owner of your Jeep Wrangler apparently disconnected and eliminated a number of vacuum hose and coolant features. Here are the vacuum circuit diagrams for your engine, you can compare what you have with these PDF diagrams: 1) for the 1989 4.2L Jeep Wrangler with a manual transmission YJ Wrangler 4.2L Vacuum Diagram.pdf and 2) 1989 Wrangler 4.2L Engine Vacuum Auto Trans.pdf for your automatic transmission equipped model. Note: The emission and carburetor circuits are closely linked together on this 4.2L engine. The ignition is somewhat independent but also works through vacuum, coolant temp and ECU timing controls. This is a complex system, the reason many owners convert to EFI. Howell, Mopar and MSD have EFI systems as you will see in the article on the MSD Atomic EFI conversion for a 4.2L. (Click on the link—there are five detailed pages to this article!) Howell is the easiest system to install and cost effective if you want to do a conversion to EFI. You can restore the BBD carburetor, vacuum circuits, ECU circuits and such; however, it will take time and patience to sort out all of the modifications and tampering that the previous owner has done to this engine's vacuum, emissions and coolant circuits. 5) The rear diff cover looks normal, it does seem like a low fill plug, but that's the Dana 35 design. The noise and hop sound like a factory limited slip differential that's either defective or in need of friction modifier and an oil change. Remove the diff cover to drain, do a thorough inspection, and if there is a factory multi-plate Spicer limited slip, there should be a tag specifying use of special lube or lube plus friction modifier. Friction modifier breaks down, and fresh oil and modifier often eliminates clutch plate chatter and wheel hopping. 6) Your engine's fuel filter should have three attachment points and fuel lines. The third line returns excess fuel pump volume to the fuel tank. This serves two vital functions: 1) reducing load on the carburetor needle and seat and 2) lowering the risk of fuel vapor lock by keeping fuel moving and not stagnating in hot lines at the engine. Vapor lock is a common phenomenon on mechanical fuel pump systems without a third pipe (fuel return) to the tank. High altitude driving and hot under hood or exhaust temperatures increase the risk of fuel vapor lock. You need to restore the 3-line system, the engine could have been experiencing vapor lock at higher altitudes under extreme load. Worth noting, poor engine performance at 3000 meters is also a function of altitude. A naturally aspirated (no supercharger or turbocharger) engine loses approximately 3-5% of its horsepower per 1000 feet of elevation. You're talking about 9,000-plus feet above sea level, so that could be as much horsepower loss as 45%! This would create a very rich burn condition on a carbureted engine, too, since the carburetor has fixed jet sizing. There is a primitive "wide open throttle" (WOT) fuel enrichment mode, which is not intended to compensate for altitude. You have an oxygen sensor on the 4.2L engine, designed to help regulate fuel enrichment (to a very limited degree) and spark timing, primarily for tailpipe emissions purposes. It does not change the air/fuel ratio constantly like an oxygen sensor helps to do on an EFI or MPI system with electronic fuel injection. In the U.S., improved high altitude operation is another reason why 4.2L Jeep owners convert from the BBD carburetor to an EFI system. EFI will instantly compensate for altitude changes and air/fuel ratio demands. This should get you started on troubleshooting and evaluating your Jeep's exhaust system, fuel circuit, vacuum circuits and carburetor. Ask questions as needed, we can take this further. Trust this helps, Alberto... Moses

One of the best lessons learned from years of instructing and our forum discussions is the value of visual learning! Now, the innovative Vimeo On Demand streaming HD video program enables the streaming of 4WD Mechanix 'Tech and Travel' How-to Series HD videos covering a wide range of subjects. Under the 4x4 hood and chassis, on the motorcycle repair stand or from the work bench, I'll deliver step-by-step, close-up HD video details for shop technicians and serious DIY enthusiasts. As you would expect, the growing list of instructional videos will demonstrate best professional practices and proven procedures for each step in the process! 4WD Mechanix Magazine and 'Tech and Travel' Forums have become an online resource for reliable technical information, in depth 'how-to' coverage and off-road lifestyle content for Jeep®, 4x4 truck, SUV, OHV and dirt bike/powersports enthusiasts. Vimeo On Demand takes viewers to the next level with streaming HD video instructional step-by-step learning! By following the steps provided in each video, viewers can perform professional-level work, save considerable cost and gain valuable insights. Off-pavement, your 4x4 truck, Jeep® vehicle or dirt/dual-sport motorcycle must be reliable and safe. Performing your own work, the right way, can increase your self-reliance while enhancing your troubleshooting skills. Projects take time to complete. The Honda XR650R motorcycle upper engine rebuild project became the first Vimeo On Demand production. The work and filming experienced the customary parts delays, machine shop sublet time and unforeseen obstacles. For this reason, all rentals are for a generous 30-day period. This added value provides the time needed for viewers to perform quality work. The 4WD Mechanix 'Tech and Travel' HD Video Series at Vimeo On Demand brings select, highly detailed 'how-to' instructional videos and backcountry travel narratives to viewers. Streaming HD videos can provide close-up, professional insights and sharp HD 1080P detail—directly from your mobile device, laptop, PC or the latest big screen "Smart" television! Watch the growing playlist of available streaming HD videos at Vimeo On Demand! Moses

Interesting...Factory Chrysler "tuning" drops the torque peak rpm down to the lower end of that spectrum...Usually, de-tuning of an engine takes powertrain stamina into account. The automatic transmission versions of these Ram truck diesels tend to get the lower performance ratings during these model years. The 46RE, 47RE and 48RE transmissions are clearly not candidates for competition "puller" torque, and that's likely the reason for the de-tuning. What's interesting is the potential horsepower and torque latent in these Cummins engines. The basic paradigm with a turbocharged diesel is that the more fuel flowing into the engine, the more horsepower and torque. Exhaust temp goes up commensurate to the amount of fuel getting shoved into the engine, so there's a limit to the power boost that the engine will tolerate. For a Cummins ISB, this is all adjusted by the tune: boost, injection timing and fuel flow. Trade-offs are that de-tuned means less power but also less EGT. Most likely in the case of light-duty trucks with diesel engines, the torque peak is also regulated to keep transmissions, drivelines and axles alive... Moses

The magazine's Honda XR650R motorcycle came to life this week! After months of sublet machine work, parts delays and time management challenges, the HD video series on rebuilding the engine top end has now finished. The camshaft choice, Hot Cams' Stage 1 type, and sublet machine work to L.A. Sleeve Company was followed by my "blueprint" assembly job and precision tune-up to match the engine changes. Learn more about the uncorking and Honda "Power Up Kit" guidelines, plus the ways to compensate for our 4,400-foot base altitude. How did this turn out?...Well, judge for yourselves fellow members! This is one incredible machine that lives up to its iconic reputation and legendary performance reputation. Enjoy the test ride, I sure did! Click here for access to the HD video. If you need detailed instructional on performing this work, I produced a nearly 50-minute 1080P HD video that has just been released at Vimeo On Demand. The very detailed how-to, step-by-step 1080P HD instructional video can be viewed from mobile platforms to big, wide-screen televisions! The Vimeo On Demand page for Honda XR650R coverage is www.vimeo.com/ondemand/hondaxr650r. At the page, you will also find an additional Vimeo On Demand how-to on valve adjustment for four-stroke motorcycle engines with conventional rocker arm adjusters. The prototype is the Honda XR650R engine. These steps are included as a "bonus" in the Honda XR650R upper engine rebuild streaming video. The 4WD Mechanix 'Tech and Travel' Series Vimeo On Demand rentals are for a full 30 day period each—rent the extensive Honda XR650R rebuild video for only $9.99 or the valve adjustment standalone video for just $5.99! Everyone runs into parts and machining sublet delays on a project...I thought it best to provide a lengthy and realistic viewing window. Case in point: The Honda XR650R was a true test of "delayed gratification". Purchased at the end of September 2013, it took until May 1st to ride the BRP for the first time! Trust you'll find the content at Vimeo On Demand valuable. I look forward to expanding the Vimeo On Demand playlist for 4WD Mechanix 'Tech and Travel' Series pages! Moses

m3out...Welcome to the forums, Martijn! The 2.5L is a popular topic at present...Your thorough description of the problem may hold a clue: The ignition is obviously involved, as the tachometer is watching for a #1 cylinder spark signal from the ECU. Before condemning any more parts or chasing down areas of concern, please check out the ground connections. We just covered this issue with another '87-'90 circa TBI YJ Wrangler 2.5L. The trouble spot was the firewall and oil dipstick ground connections. Proper ECU circuit grounding or faulty connections could be an issue. On these Jeep vehicles, electrical connections are now aging and corroding. On any 12V D.C. system, grounds are as critical as hot leads, although problems seem more prevalent on the positive side because the ground is often the body or frame on metal bodied vehicles. Grounds are critical between the engine/alternator and the frame, the frame to body, and the body to engine. Check out the grounds, they could be creating too much resistance. Look closely at the ground connection junctions, inspect the battery terminals for corrosion (check for a battery short or defect, too), and make sure that circuits like the ECU get a proper ground. Under hood heat can raise resistance in wiring circuits, and vibration can create "opens" at loose or corroded connections. This might account for your trouble while driving the Jeep. My diagnostic tool of choice for this kind of troubleshooting is a volt-ohmmeter. You can test ohms resistance over short and long wiring circuits very quickly with this tool. Even the grounds can be tested this way, using the probes between the body, frame and right at the primary ground terminals and junctions. Let us know how this works out...If the grounds are not the issue, we'll take the problem to the next level! Moses

When you note that the canister is "not holding vacuum", do you mean that when you isolate the canister and cap off all ports except the test port, the canister leaks down when you pull vacuum at the remaining port? If so, the canister is defective and may be a source of trouble. The canister is in the system to act as a reservoir for vacuum that otherwise would be insufficient to actuate the EGR. This could be a secondary issue, however, since your EGR is actually opening—though at the wrong time. The DRB-II and DRB-III scan tools can actuate devices like the solenoid as part of a test sequence. These two scan tools cost a small fortune new. (Consider the $6000 deposit on a DRB-III scan tool rental from Mopar's TechAuthority.) There are a variety of aftermarket scan tools that can run many of these same test sequences, in particular the higher end scan tools from Snap-On, OTC and others. You do need the software for your vehicle, which would be "Chrysler" and "1990". Considering the cost of these scan tools and the diagnostic labor time if you sublet this task to a shop, you might be ahead to simply find a used solenoid from a recycled Wrangler like yours and swap the solenoids. This would not cost much if we're talking about used parts, and you might learn quickly whether the solenoid is at fault. Moses

Nice work, JohnF, as you move the process along. You're really making progress here! Moses

You're welcome, DogpawSlim...Looking forward to your findings....Moses

Welcome to the forums, DogpawSlim! The best diagnostic tool for the EGR vacuum circuit is a combination vacuum hand pump and vacuum gauge. You can eliminate a lot of guesswork with this approach. A quality vacuum hand pump/gauge will last for many years. I've had the same Snap-On Blue Point pump/gauge in my diagnostics tool box since 1981. Disconnect the source hose from the vacuum canister, and cap off the other canister ports. Check the canister with a hand vacuum pump/gauge attached to the vacuum source hose. Create vacuum with the hand pump; the pump's gauge will indicate whether vacuum is holding in the EGR canister. Importantly, the signal for the EGR valve is ported vacuum, not manifold vacuum. If the vacuum source line to the EGR canister and EGR valve is manifold vacuum, this is incorrect. An EGR vacuum circuit can be routed through a TVS, CTS or CTO, or other sensors and switches, but the vacuum at the EGR valve, for both carbureted and EFI engines, is ported vacuum. Note: Some automotive EGR systems use manifold vacuum, switched on and off through either a ported vacuum signal or electrically, to open the EGR valve. The ported vacuum signal actuates the EGR in the same way as direct ported vacuum. Ported vacuum applies strongly as the throttle begins to open and not at an idle. Ported vacuum diminishes as the throttle opens widely. This means that the EGR valve opens fully just off-idle and closes as the throttle opens widely. This is optimal for EGR purposes and NOx emissions control. EGR (ported) vacuum functions like the distributor advance vacuum on older, conventional ignition distributors. Below is the Model 81 (your Jeep YJ Wrangler) 2.5L TBI diagnostic procedure for the EGR canister circuit and solenoid. I included both the overall vacuum circuit diagram and the "Fig. 37" diagram referenced in the test procedure: YJ Wrangler 2.5L EGR Vacuum.pdf Note that the vacuum source to the solenoid is the TBI vacuum port. This is not manifold vacuum. Check your hose routing, you may have a manifold vacuum source running to the EGR solenoid. The troubleshooting steps should determine whether the EGR canister solenoid is defective. If the vacuum circuits are correct and the solenoid is not defective, we'll troubleshoot the electrical signal to the EGR canister solenoid. Moses

Umm...For the stock ECM, the 1800-2000 rpm torque peak is higher than expected. This would be closer to an aftermarket tune or programming. Dyne tests by Hypertech on the program now in the '05 Dodge Ram 3500 show peak torque at 2,100 rpm; Chrysler factory programming was rated for peak torque at 1,600 rpm. My fuel efficiency sweet spot, again, is 1980-2000 rpm maximum, which would have the torque at or near peak. This is a reasonable road speed of 65 mph. It is not surprising that you would get 20 mpg at both 70 and 65. The rpm range may reflect peak torque versus lower engine speed. Typically, mileage does improve with less speed, but if torque falls off too much that is not necessary the case. In considering your quest for maximum fuel efficiency, aside from correct gearing and tire diameter, another aid is a conversion from unit hubs and the front axle constantly spinning to freewheeling hubs. A full-floating hub conversion (resembling the "real" 4x4s of a bygone era) allows use of freewheeling hubs to disconnect the drag of the inner axle shafts, differential gears and front driveline when in 2WD mode at the transfer case. Manual freewheeling hubs make this a true disconnect, and the full-floating spindles, wheel hubs and inner/outer wheel bearings offer superior load carrying capacity and lifespan. This setup also allows for periodic wheel bearing service/lubrication like traditional 4x4 axles. The frictional loss with our trucks' current unit hub bearing and axle shaft arrangement is "parasitic" drag. To what degree full-floating wheel hubs and freewheeling hubs would improve mileage is uncertain, though. The cost of the conversion is substantial and needs to be weighed. Amortizing the cost in fuel savings might take a long time. Dynatrac makes a quality conversion kit for our Dodge Ram trucks. See the link below for details: http://www.dynatrac.com/products/freespin-dodge/freespin-dodge.html Mose

Forman...I read the Pro-X instructions and recommended lifespan of rings. Before you panic, I'm guessing that Pro X is referring to dirt bikes that race, and in particular, two-strokes and four-strokes. A neighbor's son raced motocross, and the father is a motorcycle mechanics school graduate. Dad serviced the cycle and boasted that the Honda CRF250 race bike would go 40-plus hours between piston ring set changes. The only concern you have here is whether the Pro-X rings are OEM quality or better. Your KLR rings should last 15-20,000 miles, perhaps even longer on a quality synthetic oil. Even this may sound minimal, however, motorcycle engines do spin faster. When considering piston ring lifespan and wear, we're talking about the amount of piston travel. Imagine a dirt race bike on a motocross track, constantly running in the "right" gear for peak torque and horsepower, likely running the engine continuously at 6000-11000 rpm. Think of 20 hours run time in these terms, and if you do the math, that's like tens of thousands of highway miles at the cruise rpm on a KLR! If you do have a concern, call the tech line at Pro-X and ask whether the rings you have here are OEM equivalent or better in both materials and design. If so, you should be fine. Break in the 650 on a quality conventional motor oil with some Lucas zinc break-in additive in the correct proportion for the crankcase capacity. (I did this on the XR650R engine to protect the camshaft during break-in.) Once broken-in, with the rings seated, switch to a quality synthetic oil recommended for motorcycle engines. Moses

Exciting, Forman! I know this build will be a rewarding experience. We're each itching to "ride", the weather is coming around (although it snowed in the Sierra Range today, typical later spring weather). I fired the Honda XR650R yesterday and did some minor tune work and jetting adjustments at the shop today...Oh, boy! Using a Lucas zinc additive for engine break-in, running the non-silicate Honda 50/50 premix coolant/antifreeze. I decided to check the previous owner's "uncorking" measures within the carburetor and wound up cleaning metal pieces in Berryman carb cleaner. (Used the California formula to make sure that I'll live long enough to enjoy the Big Red Pig!) Ready to ride the BRP, so it's time for a dealership inspection and trip to the DMV. I'm estimating 55 horsepower (at the crankshaft) and 50-52 ft-lbs of torque. The exhaust note and throttle response with the Honda "Power-up Kit" is impressive. I did install the Hot Cams Stage 1 camshaft. Very pleased with the stable, smooth idle and ready transitions through each throttle circuit. A tip if you're running the engine unloaded (stationary) for tuning: Use a larger household or shop caged blade fan in front of the bike! This dropped engine and radiator temps 30-degrees and kept a lid on the coolant temp during the tuning today. New engine, don't want an overheat...The BRP does not use a factory fan. Future add-on? We'll continue comparing notes, Forman...Plan on a two-wheeled summer! Moses

Glad this worked out, Adam F! The ground issue is universal with EFI and often originates suddenly. Ultimately, the clicking relays were the tip-off. I'm very pleased that you now know the gremlin is gone. You'll really like power steering! On that note, be aware that the 2.5L with power steering has a step-up idle function for stabilizing the idle when exerting high loads with the power steering. The engine will otherwise want to die from the sudden boost in load, like when parallel parking or rock crawling...If you get a power steering system from a 2.5L TBI Jeep Wrangler or XJ Cherokee, note how the step-up idle system works. I trust others will value your experience and the loose ground cure. You had a roster of symptoms, yet the final fix was simple and straightforward...D.C. electrical systems: The ground side is as important as the hot side! Moses

Hi, Forman! This wear pattern may not be excessive. There may be a side-play measurement in your shop manual for judging how much the plates can move in these slots. The notches, as long as they are within the play range, should not cause an issue. With a wet clutch, you have little concern for noise or clicking of plates from play. Filing flat would not improve the function of the clutch, the plates would still shuffle around the same amount. As long as the plate tabs do not hang on the notch areas and remain within the notches' wear borders, there's not much of a problem here. On the other hand, if there is this degree of wear at the inside splines on the clutch hub, you have a problem. The inner hub takes the brunt of the torque load both on and off the throttle. Since the inner hub looks "acceptable", there's less likelihood of trouble here. I'd pass on the filing idea. As long as the clutch friction stack stays within the notch borders of the basket, and does not ramp up at the notch edges, you should be fine. As for filing, this stamped basket material should be quite hard, possibly through-hardened. (Look for signs of factory heat treating on the basket.) Filing could be not only a chore, but if you heat up the metal surface with a grinding disc, the heat treatment will be lost. This would make the metal soft and prone to rapid wear. Moses

Ah, the YJ versus the XJ Cherokee location for a Renix era ECU. Try the connections first before condemning the ECU—especially the ground points...Try switching relays, too. If the clicking pair are exactly the same rating/type, switch them and see if that does anything...Often oxidation across contacts at relays will cause enough voltage creep to start the clicking relay syndrome. So will poor ground connections. I had a "ratcheting relay" issue with the Griffin radiator relays on the XJ Cherokee that turned out to be the coolant temp sensor at the radiator. Oxidation from the stud of the coolant sensor to the sensor jacket (grounding the circuit) was a conduit for slight ground current flow at the sensor—enough to make the relays click intermittently. Modern D.C. systems often use the ground side to complete the circuit. This is typical for ECUs or PCMs when firing injectors: the injector remains positive "hot" with the key on; the PCM completes the ground side to fire the injectors. I'm using the Griffin/Spal fan relays only as an example and not being suggestive that you have an issue with the coolant sensor, though the coolant sensor is a player in your EFI system. When I cleaned the oxidation from the terminal end of the temp sensor, stud to jacket, the relays stopped clicking...Just some general info to spur your thinking, Adam F. Moses

I'm very pleased that you found a cause and solution... From your photos, the Crown bearing appears to be pressed fully onto the release bearing collar. It looks "hung up" at the end of the front bearing retainer sleeve. That must be the "step" interfering? Your bearing retainer must be smooth to the end of the sleeve, since the newest bearing works fine. You're on the home stretch, Diamond Jr...Looks like the external slave cylinder is your way to go! Moses

This sounds like a signal or contact issue. The current is trying to reach the relay but appears insufficient to hold the relay contacts closed. Poor grounds, loose connections or oxidation on connectors can cause this kind of issue. (It's not an overload, or the circuit fuse would blow.) This is more like a loose connection, bad relay, defective driven device (i.e., the fuel pump) or high resistance. To access the ECU (checking for loose connectors or whatever your plan here), look between the steering column and heater housing under the dash. See if your ECU is there, held in place with three screws...Before tossing the ECU, inspect the connector contacts for "black" oxidation. Do not scrape the oxidation with a screwdriver or sharp object, use electrical contact cleaner (Mopar makes a good one) and attempt to clean up the contacts. I use ultra-fine grade Scotchbrite and contact cleaner. Very gently rub the contacts if necessary. Before going too far here, check the ground wire junctions for the ECU and the firewall grounds! These accessible (near dipstick and at the firewall) ground junctions are notorious for building up oxidation and creating excessive resistance or worse. Humid and corrosive climates exaggerate this issue. Gauge fluctuation (you mentioned) is often a ground issue on these Jeep vehicles! Check the ground circuits for rust, oxidation and corrosion resistance... Moses

If you discover a weak or defective pump, the gauge sender is part of the fuel pump module. When you drop the tank to replace the pump, you can check out the function and ohms cycle of the gauge sender at the same time. If the sender is questionable, there are rebuilt, complete pump/gauge modules available for this application. You would be able to eliminate both problems at the same time, Adam. Again, make sure you get the lower pressure TBI pump and not a higher pressure pump for the later MPI system. Moses

At face value, Adam F, the pressure would seem way too low, accounting for the stalling and faltering under load and such. Like Stinger87 discovered, this can be either a fuel supply (pressure and/or volume) quirk or issues with the pressure regulator in the TBI unit. For troubleshooting, I'd focused on the fuel pressure and volume going into the TBI, not the return to tank. Target the input side pressure and volume. A "T" to your gauge on the input to the TBI will indicate whether you have enough pressure to the TBI inlet and the pressure regulator. My suggestions about fuel volume testing can follow from there. Return-to-tank pressure is relevant but not as pinpoint as monitoring the pressure going into the TBI unit from the tank and fuel pump—we also want to know the volume of fuel available with that input pressure. Moses

Without sounding trite, the internal slave is a "problem" only when it fails. These release bearings can last a very long time, and while working properly, they are smooth and efficient. When they fail, the leaking hydraulic fluid (DOT 3 brake fluid) can quickly ruin a clutch disk. For the most part, we only hear the negative side in this story. When the clutch gets bathed in brake fluid and slips, that's a challenging and costly issue. Servicing/replacing the release bearing requires detaching the driveshafts and removing the transfer case and transmission. The external slave eliminates this level of work if the slave cylinder leaks or fails. Hydraulic clutch release bearings have been widely used. Jeep was neither unique nor a minority when AMC introduced the use of the hydraulic release bearing in the XJ Cherokee and the YJ Wrangler. As for service concerns, from my vantage, the release bearing should always be replaced during a clutch disk and cover change out. If you keep the OE hydraulic release bearing, watch the bearing for any signs of seepage, much like you watch for a rear main seal leak or other leaks. The hydraulic fluid, being DOT 3 brake fluid, is easy to spot. If the clutch gets "spongy" or air suddenly begins to enter the hydraulic cylinder (requiring bleeding), replace the release bearing before the seal ruptures completely. Watch the master cylinder for fluid loss. Fluid height fluctuation from clutch disk wear is normal. These master cylinders can fail or leak internally, causing a soft, spongy or "falling" pedal. Hydraulic master cylinder problems prevail with either an external slave or internal hydraulic release bearing. As for the external slave, these are not an end-all problem solver either. The slaves leak and bleed down internally with wear. Again, the master cylinder is no better than the master cylinder with a hydraulic release bearing. I have built Jeep 4x4s from scratch and chose the external slave over the hydraulic release bearing. However, scrapping the OE internal hydraulic release bearing design has never been a "must" on purely stock Jeep YJ Wrangler or XJ Cherokee models. Most YJ Wranglers and XJ Cherokees only require a hydraulic release bearing change during clutch disk and cover renewal. If I were pressed to say how long the hydraulic release bearing lasts, a lot depends on how many times the bearing is operated. Driven in city traffic or constantly on crawl-pace trails, the hydraulic release bearing does wear out faster. Your call here, Diamond Jr...My two-cents worth! Moses

Bob...Sounds like you're coming up short: 0.08". The clutch cover fingers stick out further than the release bearing face in its retracted position. If the measurement is accurate, this will not work. The release bearing must move away from the cover fingers when you release the clutch pedal...a slight clearance is necessary to keep the release bearing from spinning continuously. Is the clutch disk new? Worn? The disk thickness and flywheel surface also play a role in the height of the clutch cover fingers. As the disk wears, the fingers stick out further. Of course, the release bearing must retract enough to allow for normal wear of the disk and cover finger stick-out. Your measurements might be off slightly, as we're talking about the need for 1/8" or so more clearance to allow for disk wear. The current measurements indicate that the release bearing would continually press against the cover fingers, maybe not enough to release the clutch or cause disk slippage, but surely enough to wear out the throw-out/release bearing in quick order. Let's keep working on this...There's something amiss... Moses

Not a "hijack", Adam F, we're still on topic with the 2.5L TBI troubleshooting, though this has become a long thread...That's okay, the subject reaches a lot of Jeep 2.5L TBI four-cylinder owners... An engine check light (MIL) or a stored code would help here. Are you getting a check light? For thorough testing, you'd need a DRB scan tool or an aftermarket scan tool equivalent with software that covers pre-OBD Chrysler systems. Symptoms could be a MAP or TPS issue. The TPS or crank sensor can often create these symptoms. Did you remove and wipe off the crank sensor tip? Is there oil at the flywheel? An oily or dirty crank position sensor (CPS) can be a trouble area on these engines, and your ohms test simply confirms that the sensor itself is not defective. See the exchange with Stinger87 on December 9th and 10th, this will clarify the fuel pressure and flow test method. There are other comments worth reading there. Glance through our exchanges to the 22nd of December, solutions keep unfolding here. The risk with compressed air on the supply side line is the sock at the tank. You could dislodge the sock with the compressed air. Wiser to go the distance and drop the tank, remove the pump and blow through the lines properly. I would replace the pump motor at the same time if this is the original pump. (Whether the original pump is defective or not, it has been through a very long duty cycle already.) You have the option of replacing the entire pump module or just the pump. The pump can be purchased as a separate item. A rebuilt pump/gauge module is also an option. Make sure you purchase a TBI and not an MPI pump, the output is substantially higher with the MPI (1991-up) pump, and that would cause major issues. You could clean the fuel tank and address the sock at the same time, check the EVAP hoses and make sure the rear end of the system cannot create a problem. We need to keep in mind the age of these vehicles and the amount of debris that can accumulate at the tank. Use care handling and positioning the tank. A common issue with the YJ Wrangler is shielding the exhaust pipe heat from the plastic fuel tank. You can check fuel flow on the return line, however, this will be past the regulator. If you test on the TBI input side, you will get a true reading of the fuel pump supply flow and the pump pressure into the regulator. The drain/test fuel hose size can be 5/16" I.D. for this test. I like your idea of a ball valve that is safe. It can be quickly turned off or damped down. If you have the time, keep after this, Adam F. This is a "mechanical" problem, and they always have a cause and solution. Your sharing is valuable to others, and photos are very helpful. I'm available to comment and continue making suggestions... Moses

Nice work, JohnF...Your project is a major restoration. Many of your photos reveal "before and after", and the work to date has been substantial. You're making very good headway. The result will be a whole new life for a classic, prized Jeep CJ-5! Moses