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Jeep YJ Wrangler 2.5L TBI Troubleshooting

Jeep Wrangler Jeep YJ Jeep how-to AX5

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#1 Stinger87

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Posted 16 November 2013 - 09:10 PM

Moses, your website has been extremely useful for me while working on my 1989 Jeep YJ Wrangler 2.5L TBI engine. I have used it for testing just about everything on my jeep. I have replaced several items because of extremely high emissions. Today was the 4th pass through the test, and I finally passed my emissions test.

 

I have replaced the ignition coil, ignition control module, spark plugs, cap and rotor and set the base timing, map sensor (because it did not hold vacuum), coolant temp sensor and my fuel injector. With all of that, my emissions finally were within spec.

 

I am still having a loss of power issue with my jeep, and the only thing that helps is when I run Seafoam through the vacuum lines. It helps for about 2 days and then the same issue. Any ideas would be extremely helpful. One possible clue: The wide open throttle switch is in-op (cannot locate the part), and my throttle position sensor does not put out a signal if this helps any.

 

Stinger87 (Josh)



#2 Moses Ludel

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Posted 16 November 2013 - 09:42 PM

Thanks for the compliment, Josh.  The TBI signal could be a factor, although the Seafoam has me looking at the oxygen sensor, EGR valve or an exhaust obstruction...The '89 YJ Wrangler is early OBD and awkward for testing the onboard diagnostics.  If you do have access to a scan tool that will work with Chrysler's early OBD hookup, try getting a DTC trouble code from the ECU.  You do have a diagnostic test plug on the Jeep engine bay wiring.

 

Make sure that the exhaust is unrestricted, and consider the EGR valve and oxygen sensor.  Test parts before replacing them.  Even though the oxygen sensor is a higher mileage "perishable", you should still make sure that it is defective before buying a new O2 sensor.  Same with the EGR valve. 

 

As the issue goes away when you sweep Seafoam through the vacuum hoses, this may be a clue.  Seafoam flows through the combustion chambers and exhaust, which may be cleaning a sticky EGR valve or dirty O2 sensor.  Unseated and stuck open, the EGR will generally cause a rough idle or low speed performance quirks.  An EGR valve stuck shut will create upper cylinder heat and possibly erratic fuel mixtures.  The EGR controls NOx and can affect other exhaust gases. 

 

Considering your troubles to this point, the EGR valve would be worth testing.  If you have a hand vacuum pump, you can quickly test the EGR with the engine idling.  Attach the pump hose to the EGR.  Pump down vacuum with the engine idling, enough to open the EGR valve.  You should hear a change in engine speed and smoothness as you open the EGR valve at an idle.  No changes would indicate that the EGR valve is either stuck or defective.  The valve has a diaphragm that can be weak or leak with age.

 

Be cautious when working around the EGR valve, it gets very hot!  Handle with care...If you attempt to remove and clean the EGR valve, do not soak the diaphragm in solvent or carburetor cleaner.  Try to submerge the base of the EGR valve (metal parts only) in carburetor cleaner, and make sure you get the valve plunger to open and shut freely—and seat completely.  Rinse away any solvent or carburetor cleaner before reinstalling the EGR valve and running the engine.

 

Moses


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#3 Stinger87

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Posted 17 November 2013 - 01:42 PM

Good afternoon Moses...Thanks for the quick reply, and I forgot to add that I did replace the egr valve even though my old one was good. I replaced because I got a good deal on it and it looked ancient. I had the jeep running really well but I did notice that a few days after I changed the fuel pressure regulator that is when I had the idling issue.

 

The regulator removed my issue of the loss of power but now it just feels as if it were about to stall during stop lights and when in neutral idling. I installed the old fuel pressure regulator and the hard idle and loss of power issue are there. Tomorrow I will throw the new regulator in and now I just have to sort out the idling issue.

 

I had a local exhaust shop test my o2 sensor and inspect my exhaust for back pressure and to see if my cat was plugged but they both passed. The only things I can think would be my idle speed control which does work. When I start the jeep up my rpms go to about 2000 and then idle around 1000 but then seems the engine starts to sputter like it's not getting enough fuel. As soon as I give it some throttle the engine wakes up and runs smooth. Thanks again with the quick reply.

 

Josh



#4 Stinger87

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Posted 17 November 2013 - 04:40 PM

Good evening...Another thing i was curious about is the thermostat on my jeep. From my understanding it should have a 195 in it. My gauge at times tells me different because it seems like it is running around 165-175 on an average sometimes the temp will spike to where it looks close 200 and that is when it runs the best . I am guessing this would cause an issue with the computer and not allowing the engine to go into a closed loop to properly function properly. I was actually looking to swap that out to make sure that it is running correctly at 195. i was wondering if anyone had anything to add to this?

 

Another thing is for my previous comment about my rough idle. I did a ohms test on my intake air temp sensor and cold it was close to 2000 ohms. I do not know the specs for this but to me it sounds out of range. While the engine was at operating temp or to what the gauge says about 165-175 the ohms rating was around 1500. If anyone had any insight of this or any more knowledge about the IAT that would be great. Thanks again for any help and hopefully this all can help someone later on.

 

Josh 



#5 Moses Ludel

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Posted 17 November 2013 - 06:05 PM

Josh...Glad to see your follow-up, I'm focused on your second post as possible ties to your problem.  For openers, you're absolutely right, the engine will not come out of cold start mode if the IAT is out of sync or the engine coolant temperature is off.

 

Jeep constantly emphasized a 195-degree F thermostat to assure adequate temp for the closed loop mode as you comment...Definitely replace the thermostat unless you suspect that the gauge is inaccurate—I like to use a surface temp IR tester to check the actual temperature.  You can temperature probe around the engine block, at the radiator, hoses and, importantly, at the thermostat housing.

 

As for testing the IAT (actually called the manifold air/fuel temp sensor or MAT), here are the specs for your '89 TBI system:

 

Degrees F   Ohms

212              185

160              450

100            1600

  70            3400

  40            7500

  20          13500

    0          25000

 

The two adjustable features on your TBI are 1) the TPS (throttle position sensor) and 2) the idle speed actuator motor or ISA.  Have you adjusted either of these devices?

 

Moses



#6 Stinger87

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Posted 18 November 2013 - 04:44 AM

Good morning sir,
 
I will double check the MAT sensor tonight and log my readings. The TPS sensor when i losen it and rotate it i still get zero signal out of it so i am assuming that is part of my issue. The idle speed actuator i do not know how to adjust unless it is just turning the threaded part of it. Today i drove the jeep to work with the bad fuel pressure regulator in it and it drives decent. Enough power through all gears but sputters a little bit around 1500-2000 rpms. At red lights and stop signs the motor will idle down to 1000 rpms and sounds good but then drops to about 500, it does not stall but it does sound rough. Even sometimes at 1000 rpms the tac and engine jump around and this idling issue just started happening once i put the new fuel pressure reg in it. I ensured the TBI was clean made sure that the 4 vacuum lines were in good shape no cuts or anything. I also replaced the TBI gasket to make a good seal. Last thing i noticed was unplugging any of my sensors did not effect the way the vehicle ran anymore such as MAP sensor MAT. The MAP sensor used to shut the vehicle down but it doesnt effect it anymore.



#7 Stinger87

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Posted 18 November 2013 - 11:02 AM

Alright so i did some troubleshooting. In my previous post i said that this all happened after i installed the new fuel pressure regulator. I left out one key detail. I ordered this regulator from Rockauto and the spring that they gave me did not have enough resistance on it but i used it anyway thinking it should work since it's new and they sent it to me. Wrong.... it actually flooded the engine with so much fuel and back fired out of the intake with this happening i'm almost certain that damaged the MAT sensor causing the rough idle. My issue now is actually locating the MAT for a 1989 and Chrysler is saying that it has been discontinued. I have found a similar sensor for a 91 the only difference is the way it is wired up but it still is a two wire. Right now i am looking at getting the sensor for the 91 and buying a few snap together connectors and making my own harness for it.



#8 Moses Ludel

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Posted 18 November 2013 - 05:32 PM

Josh, if you do get the later MAT, you need to compare the ohms settings and make sure they're right.  1991 is definitely an MPI engine, not TBI, Chrysler discontinued TBI after 1990.  Here is the OEM Mopar part number for your MAT sensor:

 

33002382 SENSOR, Intake Air Temperature

 

This part also fits a 1991 3.0L Dodge Monaco V-6.  It has been discontinued by Mopar.  However, I found this remarkably lengthy cross-reference chart courtesy of a Google Search.  Verify the cross-reference.  The Chrysler number above is from my set of Mopar Catalogs and is reliable.   If the part numbers below do cross over (verify before buying), we can thank "Hornbrod" at the Comanche forum http://comancheclub....t-a-mat-sensor/ for this effort: 

 

AIRTEX 5S1004
AUTO-TUNE PT9599
BIG A 53-1009
BORG WARNER WT5502
CHRYSLER 33002382
ECHLIN TS5016
FILKO CS-62
GP/SORENSEN 779-19015
KEM 139-411
NAPA TS5016
NIEHOFF TS81351
NIEHOFF WA629EL
STANDARD/HYGRADE AX9
TOMCO 12120

WELLS SU330          

 

Let me know what works here.  If you decide to set the ISA, I have the OEM specs, let me know...

 

Moses

 



#9 Stinger87

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Posted 18 November 2013 - 06:24 PM

I currently have a MAT for a 91 on order which will be in tomorrow morning so i will compare the ohms readings and post them on here tomorrow. In addition if the ohms readings are the same.Here is the current part number that i will be trying tomorrow that is the closes match to what i am currently running MPE TS5014TB this here is a Napa prolink number and i am not 100% sure that it will work but i will verify tomorrow and keep you updated. All of the crossover number that you posted Moses i could not find anywhere. I am not sure if it is because its not the full part number but i even tried to interchange those part number through several other sites and i couldn't find anything. Anyway tomorrow i will have an update. Thanks again for the help its much appreciated.

           

#10 Moses Ludel

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Posted 18 November 2013 - 11:24 PM

These are all national brands and available product lines, whether the specific part numbers are still active is another story.  Try the NAPA number at your local NAPA store.  See if Rock Auto carries any of the other lines, and if so, whether they can furnish the part from their Warehouse Distributor sources.  There are way too many numbers here to strike out...eBay might be another source, Josh.

 

Also, check the individual product lines, as most should have an online catalog at their official website.  Search by part numbers and manufacturer at Google.  See if that yields anything...As for the part you ordered, the oddball 1991 Dodge Monaco 3.0 V-6 listing suggests that some Chrysler engines were still using this MAT after 1990.

 

Moses



#11 Moses Ludel

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Posted 18 November 2013 - 11:27 PM

Regarding the rough idle, have you tried finding a vacuum leak?  Have you changed the PCV valve?  Back to the Seafoam temporary fix, the PCV valve could be involved...The valve is a routine replacement service part.

 

Moses



#12 Stinger87

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Posted 19 November 2013 - 04:32 AM

Yes sir, i changed the PCV valve on my oil change which was about 200 miles ago. As for vacuum leaks i havnt not found any. While the motor was cool i used carb cleaner and sprayed the hoses to see if the rpm would fluctuate but i didnt get any findings. When i reinstall my fuel pressure reg i will replace the 4 vacuum lines on the TBI. I didnt get to do any more troubleshooting lastnight but i will pick up my sensor and see what i can do tonight



#13 Moses Ludel

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Posted 19 November 2013 - 04:02 PM

Let's see what that MAT does...You'll check ohms range first...The carb cleaner usually turns up leaks.  We'll stay after this, there's always a reason for the hunt-and-peck idle!

 

Moses



#14 Stinger87

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Posted 19 November 2013 - 04:13 PM

So I have the new mat sensor and the ohms readings are very low 10.5 ohms but the jeep is idling good. I am going to use this since it is running better then with a broken sensor in it. I will post a better part number once I cross ref another. I tried to add some picks of the new sensor wires up just have to see if they load. Tomorrow I will put the new pressure reg in it, I had to order another since my wife tossed the other one on accident haha. Also on my drive to work tomorrow I will get the engine nice and warm and see if the sensor keeps the engine running good or it if goes way out of spec. More updates tomorrow!

 

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#15 Moses Ludel

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Posted 20 November 2013 - 12:05 AM

Gotcha, Josh...Can see the plug and wiring differences.  Suggestion for your use and others: When working with an EFI system, I use solder for splices and cover with multi-layers of heat shrink tubing, enough tubing to emulate the insulation strength at the wires.

 

EFI circuits are hypersensitive to ohms resistance, and with a sensor like the MAT, Josh, ohms resistance accuracy is critical.  When we use a butt connector and crimp approach, there's a lot of room for ohms mismatch.  The crimp, by design, simply cannot lock all strands of the two wires together.  Also, vibration is clearly an issue with any automotive application, more so with a Jeep 4x4.

 

I always use rosin-core solder on electrical splices like this.  Flux helps, easier in the core so you can solder steadily.  Consider soldering, it's really quick in the long run, and you'll take the guesswork out of ohms resistance.  (Crimping can often work okay for trailer lights and such, I still prefer solder.) 

 

Another very good feature of heat shrink, when done properly, is to prevent corrosion wicking up the wires.  A 4x4 Jeep gets wet, let's face it, that's what a Jeep does!  So, preventing water from wicking up wires will go a long way toward eliminating corrosion over time.  Again, a good reason to use rosin-core solder and heat shrink tubing! 

 

As a footnote, when I bring the two wires together for soldering, I face the stripped wire ends toward each other and try to lap and interlace the strands evenly.  Solder can fill tiny gaps and secure the wire joint together.  Keep strips of heat shrink well up the wires, away from heat, while soldering.  Then slide the heat shrink into place and shrink it.  Wooden matches (move quickly or hold away from the tubing) work well for me when shrinking the tubing.  Use care not to melt through plastic!  I know the joint is laced and soldered properly when the finished "bulge" is minimal.

 

Moses



#16 Stinger87

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Posted 20 November 2013 - 04:35 AM

I am having all of those sensors crossed and i cannot find a single one because they are discontinued.



#17 Stinger87

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Posted 20 November 2013 - 05:52 AM

Here is a good post about this same issue if anyone was wanting to read up some more on it.

http://www.jeepforum...gh-how-1549148/



#18 Moses Ludel

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Posted 20 November 2013 - 07:03 AM

Josh, I read the post at the Jeep Forum/link.  The Jeep owner used a Wells unit that also fits a later application.  It sounds like your approach has its match.  If your ohms readings are correct for the '89 specs I furnished, you bought the right sensor and simply needed to modify the wiring...See my comments about soldering, your best assurance of ohms integrity.

 

We should have reverse engineered the switch by ohms rating in the first place then sought out a two-wire replacement sensor with the right thread pitch and ohms readings.  Apparently, Chrysler and Renix MAT sensors have reasonably close ohms tolerances, maybe other applications, too...Good job, Josh!

 

Moses



#19 Stinger87

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Posted 20 November 2013 - 03:37 PM

Alright so i just picked up my new fuel pressure regulator from advanced auto because they had the fastest delivery rate. I took the tbi off to get to the regulator and installed the new FPR. Reassembled everything but i look the tbi cover off so i could see the spray pattern and check for excess or not enough fuel. Crack the motor over and the engine spikes to 3k rpms so i get out to look at it and fuel was spraying out of the bowl. I shut the engine down cleaned up the fuel and figured i would try again. Cracked the engine over but it didn't start. Assuming the engine was flooded i figured it was a bad regulator so i took it all apart again and installed the old one. Once i re installed everything i cracked the engine over again and it fires up and runs perfect......I am drawing a blank because the idling issue is gone and it doesn't sputter. I did check the ohms for my new IAT/MAT sensor and at operating temp my sensor was at 1780 ohms which doesn't seem in spec but as of right now its running with no issues. That may change in the morning when i drive it to work and put a load on the engine. as of right now i am running out of ideas



#20 Moses Ludel

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Posted 20 November 2013 - 04:50 PM

All interesting, sounds like the first regulator had a plugged passage or flow.  The trip up to 3000 rpm should have cleaned things up, and you did do a removal and replacement of that first regulator (now in place again)...You'll know in the morning, also whether the MAT ohms rating will work...Moses

 

P.S.:  If this does work out, great...Otherwise, you're back to the drawing board...Clogged or blocked passage would be the only explanation for a "cure".



#21 Stinger87

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Posted 21 November 2013 - 09:32 AM

As of right now i have not had any issues with the jeep (knock on wood). It is idling at 1000rpms and drives good and doesnt bog down when stopping at red lights or stop signs.



#22 Moses Ludel

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Posted 21 November 2013 - 10:20 AM

Really good news, Josh!  When you have time, post some pics of your '89 Jeep YJ Wrangler at the 'Tech and Travel' Forums...Looking forward to your posts...Welcome!

 

Moses



#23 Stinger87

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Posted 22 November 2013 - 02:05 PM

Haha so the jeep drove good this morning and then this afternoon it was running like hell. Attempted to drive it home since I only live about 5 miles away and got outside of work and it died. Cranked it over a couple times and still no start. Called a tow truck and waited for it to come but every 5 minutes I would crank it to test my luck. After about 40 minutes it did finally start and I hauled ass home it was bucking and jerking like crazy. I figured it is the fuel pump since it is pretty much the only thing in the fuel system that hasn't been changed. Should get the pump tomorrow and I'll drop the tank and go from there.

#24 Stinger87

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Posted 23 November 2013 - 04:08 PM

Installed the new fuel pump this morning and fired the jeep up. It ran but barely. I don't have a fuel pressure tester but the i took the tbi cap off and looked in the bowl and the injector was spraying so much fuel. Also black soot was coming out the back kind of looked like a diesel truck. It sounded like it was missing really bad too so i shut it down. inspected the butterfly valve and opened it up and the intake had a puddle of fuel in there. I am not sure if it is in limp mode because none of the sensors determine how it runs. If it is running and i unplug the map sensor it used to shut the jeep down now it no longer does this. I took the spark plugs out and they were black and wet so i let them dry and cleaned them off. Now the jeep doesn't run at all unless i wait about 45 minutes after it running. This little guy is turning into a nightmare. Probably taking it to a garage this week...... 



#25 Moses Ludel

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Posted 23 November 2013 - 05:58 PM

Josh, before you throw in the towel, let's look at this objectively.  You had no spillage or flooding issues before you changed the pump.  You have severe flooding issues now—and are likely in limp home mode as a result.
 
The 2.5L fuel pump for a 1989 Wrangler is a Walbro 550 or Chrysler 83502995.  Here are the 2.5L TBI pump specs: 

1989-1990 Jeep Wrangler Fuel Pump 4 Cyl. 2.5L (E) E.F.I.
 

OE spec Walbro electric fuel pump and installation kit fits directly into any 1989-1990 Jeep Wrangler 4 Cyl. 2.5L (E) E.F.I.. Detailed fuel pump installation instructions included. Made in the USA.

Fuel Pump Specifications
Walbro Part Number: 550
Minimum Current: 12 Volts
Operating Pressure: 17 PSI
Minimum Flow @ Outlet: 28 GPH Low Pressure
Fuel Pump Location: In-Tank

 
Now, let's look at a 1991 2.5L MPI fuel pump for a Wrangler.  It will fit your tank fine, as '87-95 tanks are similar.  This is a Mopar pump #04637193.  Here are the specs for the Walbro common equivalent: 

1991-1993 Jeep Wrangler Fuel Pump 4 Cyl. 2.5L (P) E.F.I. (Chrysler #'s 4637192 & 4637193)
 
OE spec Walbro electric fuel pump and installation kit fits directly into any 1991-1993 Jeep Wrangler 4 Cyl. 2.5L (P) E.F.I. (Chrysler #'s 4637192 & 4637193). Detailed fuel pump installation instructions included. Made in the USA.
 
Fuel Pump Specifications
Walbro Part Number: 5CA234
Minimum Current: 12 Volts
Operating Pressure: 65 PSI
Minimum Flow @ Outlet: 24 GPH High Pressure
Fuel Pump Location: In-Tank

 
Note the obvious pressure output differences for these two pumps that look similar.  The '91-up engine is MPI and operates at 31 PSI (regulated) injector pressure.  Your '89 TBI operates at a 14-15 PSI (pressure regulated) setting.  If you put the later pump into your tank, you will be pushing 65 PSI against a TBI pressure regulator designed to operate with a 17 PSI tank pump pressure.
 

This is likely your newly developed flooding problem.  My hunch: The new pump supplied is for a '91-'93 MPI engine, not your TBI application.  If you run a pressure check on the pump-only, you will likely turn up a 65 PSI output pump.  This would over-pressurize the TBI pressure regulator and cause flooding.
 
Check the new fuel pump part number and run the number at www.fuelpumps.com.  This is where I came up with pump output ratings for TBI versus MPI engines:
 
http://www.fuelpumps...efi-p-2212.html
 
http://www.fuelpumps...193-p-2210.html

 

Before dropping the tank again, I would run a pressure check of the fuel pump (before the regulator, pump-only pressure).  If you are confident this is the wrong pump, either by the part number or actual pressure tests, drop the tank and replace it with the correct, 17 PSI output pump.

 

Let us know what you find here...TBI and MPI requirements are dramatically different...
 
Moses



#26 Stinger87

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Posted 23 November 2013 - 07:25 PM

I just cross referenced the two numbers and the pump for the 89 is the one that i got from Napa. I even cross referenced the Chrysler number for the 91-93 to see if the same pump came up and a different one did come up. A different pump did come up so as long is Napa is correct on their number then i do have the correct pump for a 89 TBI. Something happened to make the jeep run like this all of a sudden because Friday after work it was running terrible too and the engine sounds about the same as it does now. Only difference is i didn't open the tbi cap to see the amount of fuel that it was using on Friday. I am not sure if i am having a complete ECM/ECU failure of some sort. The emission shop that i took it to did say that the jeep was going in and out of Open closed loop erratically and they couldn't pin point the issue. They said it was dumping about 5x the normal amount of fuel and only going into closed loop for about 3 seconds and then right back into open. Right now it is running so rich that it floods the motor and will not allow it to start until the fuel in the intake evaporates. I have changed every sensor on the jeep except the oil pressure sensor. I have never had this many issues with any vehicle and i have been a mechanic for about 7 years now (heavy equipment so i guess this doesn't really help my cause haha). Back to the fuel pump, i dropped the tank and took the old pump out and the sock was not attached to it and it was laying at the bottom of the tank. Also the old pump had so much gunk and grim clogged up in it i swore the new pump would fix it but it didn't. One other thing that i will fix in the morning and i just thought of is the fuel tank vent line was just dangling before i dropped that tank so i don't know if that is the culprit or not. I know it is supposed to be linked to the evap canister but i will find the loose hose and hook it up in the morning and retest everything. Something that still doesnt make sense is how none of my sensor have any affect on how the jeep runs now. MAP, MAT, CTS, TPS i can have them all unplugged and it just runs like it does even if they are plugged in.  :huh:



#27 Stinger87

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Posted 23 November 2013 - 07:28 PM

could contamination have jacked up my fuel pressure reg? Once i installed the new pump and saw the sock was not attached i replaced the filter as well....



#28 Moses Ludel

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Posted 23 November 2013 - 09:07 PM

I was about to ask if you changed the filter...The sudden stalling and inability to start could have been a filter issue at that point.  If the filter was bad enough from sucking debris off the tank bottom, it may have disintegrated and clogged the pressure regulator.  Recall, you did have one point where the removal of the regulator and reinstalling it seemed to help...I commented that the pressure regulator may have had a clogged passage that cleared. 

 

Debris like you describe, from either the sludged tank or a filter coming apart, could create fuel flow issues or clog the TBI fuel inlet, pressure regulator or ports/passageways within the TBI unit.  As professionals, we don't like to borrow trouble, right?  So, my approach is always systematic and aimed at eliminating immediate symptoms.  Here's what I would do now:

 

1) Confirm fuel pressure from the pump, making sure it is within the 27 PSI or so maximum.

 

2) If the pump pressure is correct, I would verify fuel pressure past the regulator.  It must be limited by the regulator to 14-15 PSI.

 

3) Once you have uniform fuel flow at the regulator in terms of volume and pressure, turn to the passages in the TBI unit, between the pressure regulator and flow nozzles.

 

4) An often overlooked sensor that can create a lot of trouble is the crankshaft position sensor at the back of the engine on the upper bellhousing. Oil and debris can cause this sensor to malfunction or work intermittently. Many overlook this as a trouble spot and chase after other issues.  It takes only minutes to access this sensor, remove it, and clean it thoroughly with spray carburetor cleaner and a rag.  If in doubt, do an ohms resistance test on the device. 

 

Make sure you do not have too much fuel pressure past the regulator.  If pressure is high, determine whether this is a pressure regulator malfunction or a fuel pump with excess output pressure.  You had many times that the engine ran well then suddenly went into some form of fuel flow failure: too little, too much, etc. 

 

Note: At this point, with all of the flooding, the oxygen sensor and catalytic converter may be overloaded.  You may need to clean that up to restore a normal idle and closed loop functions.

 

Overall, though it costs for diagnostic equipment, you likely could benefit from a search for DTCs.  A DRBII or aftermarket scan tool (Snap-On or OTC Genesys) with hook-ups for the Jeep TBI era could prove helpful.  Any code reader that would hook to your diagnostic plug could at least retrieve stored codes from the ECU.  Look for an inexpensive code reader for your pre-OBDII era Jeep.

 

I'd be surprised if you have no stored codes at this point.  I would clear the codes and get a fresh read, as there could be several sets of stored codes with some problems already remedied. 

 

At this point, I'm thinking a dirty crankshaft position sensor, high fuel pressure or a fuel pressure regulator malfunction.  Functions of the ECU typically work or they don't; seldom do they work intermittently, which makes me think in terms of a "mechanical" device rather than electronic.  (I would, however, check wire connectors for corrosion and contact integrity.) 

 

 As you share, you've exhausted a variety of sensor possibilities, not to mention your wallet, chasing this around.  Onboard diagnostics and fuel pressure tests can demystify and at least confirm or eliminate trouble spots.  Stop the flow of money over the parts counter until you're absolutely certain you have a malfunctioning part...

 

Unless you've exhausted your tools or patience, there's much to be gained by following through.  Be systematic like your heavy equipment repairs and troubleshooting.  When you do find the culprit and fix it, you'll have far more trust in the Jeep.

 

Moses



#29 Stinger87

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Posted 24 November 2013 - 02:12 PM

Alright so here is what I got. Took the tbi off the and the regulator is wrecked. The regulator has a bubble and tiny rip in it. There was also a little debre in the regulator bowl. Hopefully with the new regulator it should be good getting tired of replacing the regulator haha. I took some pictures for everyone to see and I'll load the picture of the gunked up fuel pump

Attached Files



#30 Moses Ludel

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Posted 24 November 2013 - 02:57 PM

Oh, boy!  Did you flush out that fuel tank?  I've seen more "troubles" with fuel tanks and gunk since the ethanol era.  Left to its own devices, ethanol damages plastic screens, dissolves things like pickup socks, clogs motorcycle (and automotive) carburetor jets and passageways, you name it!  Maybe corn farmers made it big on the ethanol bonanza, consumers certainly didn't...

 

So, you're back on the repair trail and narrowing the fix here.  Good job, Josh!  Thanks for sharing the photos, quite graphic!  Looking forward to the next update...

 

Moses



#31 Stinger87

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Posted 24 November 2013 - 05:22 PM

I didn't flush the tank because it is less than a year old and I don't really have the resources to do so where I currently live (apartment). I am sure there is some gunk in there but I hope this will do for now. I got the new pump and pump sock on. New fuel filter and a new regulator and tbi gasket coming here soon. I probably won't have another update until after thanksgiving but I'll keep you posted once I get everything in.

#32 Moses Ludel

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Posted 25 November 2013 - 11:25 AM

Happy Thanksgiving to you, friends and family, Josh!  You're going to have a very reliable '89 Jeep YJ Wrangler 2.5L four-banger when this is all done...

 

Moses



#33 Stinger87

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Posted 30 November 2013 - 10:19 AM

Good afternoon,

 

Thanks for the holiday wishes and i too hope you and everyone had a good time during the holiday. Today i installed the new fuel pressure regulator and the jeep runs but it sounds like its getting to much fuel. Im not sure if something went up and is holding the injector open or not but i can actually unplug the injector while the jeep is running and the jeep runs better..... I didnt do to much digging into it today other than the new fuel pressure regulator and tbi gasket then fired it up. Alot of smoke came out of the tail pipe and the engine was rocking pretty hard like it was missing but it just looks like way to much fuel is spraying. And im not sure why the injector still works when unplugged.



#34 Stinger87

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Posted 30 November 2013 - 12:00 PM

changed the fuel pressure regulator spring and fired up the jeep and it seems like it was running rough but better so i checked the spray pattern and it was spraying and it had a drip too so i pulled the injector out to clean it with carb cleaner. Cleaned it up and just did what i could to clean and install it. Fired up the jeep and it was running good so i started cleaning up my tools and then i reved the engine a little about 2-3k rpms and then it stalled and wont fire back up. When you crank the engine white smoke comes out of the intake. Gonna let it sit outside in time out for a while to think about its actions.... ill do some more research later and see what i can figure out. One more thing alot of black soot blew out of the tail pipe too and covered the side walk.



#35 Moses Ludel

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Posted 30 November 2013 - 06:25 PM

Has been running very rich, and the oxy-sensor may be sooty, too.  Could pay to remove the O2 sensor and clean it a bit, at least inspect it and wipe off soot.  The engine has been through the ringer with over-rich mix, you're likely sorting out the impact of all that fuel flowing through.  Spark plugs could also be sooty at this stage...

 

As for the "injector still works when unplugged", that's a good one.  Makes me want to run a pressure check of incoming fuel pressure to the regulator.  If this over-fueling persists, the regulator may be unseating from too much incoming fuel pressure, which I hinted about earlier.  Time for an actual fuel pressure test on that inlet pressure to confirm the fuel pump output?

 

I'd check the spark plugs and oxygen sensor for soot...

 

Moses



#36 Stinger87

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Posted 30 November 2013 - 09:16 PM

I will check harbor freight or rent a fuel pressure tester from auto zone. Something I was thinking earlier, I traced the old fuel pump to a 91-95 fuel pump and I have no clue about the old regulator because the springs are totally different. The old regulator had a heavy duty spring and the new regulatory was a very easily compressed spring. Today when I installed the new regulator I used the old regulator spring and it ran like hell and was pouring fuel even with the injector unplugged. I installed the new spring with the new regulator and it ran better but I didn't test to unplug the injector which I will do in the morning. In earlier posts I mentioned none of the sensors worked either but that I think is because I had so much fuel pressure that the sensors could not cause the engine to cut off because of the fuel air and spark ratio. I will post again tomorrow with some more info about all this. Attached are the new and old springs for the regulator. The old spring Is the large one and the new one is the small one which seemed to help with the fuel pressure. The second photo is the black soot that blew out the back.

Attached Files



#37 Stinger87

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Posted 01 December 2013 - 12:38 PM

I didnt do a fuel pressure check on the jeep but everything is working as it should now after putting the new regulator and spring in. The injector no longer fires when unplugged. Im thinking it had excessive pressure and forced it to open and fire. So as of right now the jeep fires up and runs pretty good i didnt get to take it out for a drive but tomorrow i will get some fuel and i think im going to seafoam the vacuum lines again to clean all the sensors. I also think im going to get a second bottle of seafoam to run in the crankcase because i have a squeaky lifter which does go away after its warmed up. I also think this will be a good idea just because of how rich it was running to help clean out all the carbon build up. ill post back again tomorrow and let you know the results. As of now i am thinking that my issues is resolved but i want to run it for about a week to make sure.



#38 Moses Ludel

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Posted 01 December 2013 - 02:55 PM

Wow, that spring comparison is graphic, thanks for the photo!  The wire size on the smaller spring must be 1/4th the apply pressure...Apparently, there was excessive fuel pressure, and the leaking or by-passing regulator was "force feeding" the injector without the normal electronic opening and closing of the fuel flow. 

 

Good observation, and good solution...Let's see where this leads now that the engine is flowing a more moderate amount of fuel.  We'll see if the sensors are all back on line with normal closed loop function and air-fuel ratios.

 

Moses


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#39 Stinger87

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Posted 02 December 2013 - 01:15 PM

well back to the drawing boards...jeep now idles decent until warm then bounces from 500-800 rpms. also bucks really really bad when driving! maybe look at timing again tomorrow or when the engine cools down. This little guy is a nightmare haha



#40 Moses Ludel

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Posted 02 December 2013 - 02:22 PM

Lean or like a timing issue?  Possibly, Josh...However, I'd check the TPS voltage reading.  This device is adjustable on the 2.5L four.  Unstable idle and bucking could very well be remedied by a simple TPS adjustment or repair.  Don't rule out the ISA motor adjustment.  Might as well check the WOT adjustment, too!

 

To demystify this, I've copied the 1989 factory manual information on adjusting each of these devices for a 2.5L TBI.  Open the PDF for details!

 

Attached File  Jeep 2.5L TBI TPS ISA WOT Adjustments.pdf   2.35MB   33 downloads

 

Moses



#41 Stinger87

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Posted 02 December 2013 - 04:57 PM

thanks for that Moses, tomorrow morning i will run those tests to make sure the adjustments are in spec. one more thing i forgot to add is other than the slightly rough idle it runs and revs fine until i put a load on it/ drive. it was still dropping the rpms really low when coming to a stop.



#42 Moses Ludel

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Posted 02 December 2013 - 08:44 PM

Try the TPS and other tests, this could narrow it down.  With all of the changes in fuel pressure, a new pump and regulator and so forth, there could be room for a TPS adjustment or ISA setting...WOT is simple to confirm.

 

We always like it when there is something concrete to address.  You've found several sources of trouble lately, Josh, on the right track!

 

Moses



#43 Stinger87

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Posted 03 December 2013 - 08:20 AM

Alright it seems like my tps sensor is bad. The most voltage I can get out of it is 1.7v unless I fully open the butterfly valve then it goes up to 4.1v. The book doesn't say to test with a wide open throttle or just sitting there as if it were idling so I'm not sure if it is bad or I'm just testing it wrong

 

i tried adjusting it but the voltage would only go lower down to like .5v



#44 Moses Ludel

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Posted 03 December 2013 - 08:56 AM

The factory method looks for a percentage or ratio as indicated in the PDF...If you followed the steps, you're getting useful feedback!  The TPS (Throttle Position Sensor) is like a rheostat or potentiometer: as the throttle valve opens, the voltage goes up proportionately, engine idle being a specific baseline voltage.  This signal is crucial for the A/F ratios, idle performance and to achieve a balance throughout the EFI system. 

 

Since the TPS gets a real workout (consider the switching cycles here!), this is often a trouble spot on higher mileage EFI engines!  If you can narrow this to a defective TPS switch by accurate testing, you've hit the mark!  If you confirm the TPS failure, you have a very tangible source for the trouble you describe...Sometimes, the TPS can be adjusted, but if it is finicky and not holding an adjustment, it's defective.

 

This is what I like about mechanical things.  There's always a reason why they work or don't.  (Human beings are more complicated.)  Keep us posted, Josh! 

 

Moses



#45 Stinger87

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Posted 03 December 2013 - 09:05 AM

im going to say that it is worn out then. It is very old looking and was covered in dirt possibly causing to much resistance on the inside causing the low voltage. im going to purchase a new one hopefully get it today from the Napa distribution center up the road then i will compare voltage and post the readings that i am getting.



#46 Stinger87

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Posted 03 December 2013 - 09:12 AM

The book says i need to be around .935 or 93% and with my output reading of 1.7 and my input voltage of 5.1 volts i was no where near that. 1.7 divided by 5.1 gave me .33 repeating or 33%. I am determining that this is a faulty tps sensor so i will get a new one and retest and adjust to put the tps within factory settings.



#47 Stinger87

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Posted 03 December 2013 - 11:45 AM

Well i installed the new TPS sensor and the max that i could adjust it to was 1.9 volts but under wide open throttle it is at 4.7 volts which does cross over to .92 when divided by my input voltage of 5.1 is almost spot on. Fired up the jeep sounds really good reved good with no issues so i took it out for a drive. It was doing decent seemed to be lacking on power and about half way around the neighborhood it started sputtering/ bucking not as bad as before and coming up to stop signs it would still drop to about 500 rpms and bounce around. 



#48 Stinger87

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Posted 03 December 2013 - 11:59 AM

went back outside to tinker around and noticed with the key on engine off the injector drips and i don't think this should happen and its a new injector so i hope it didnt get ruined from all the debris that ran through the system from bad pump. that's all i got for now



#49 Moses Ludel

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Posted 04 December 2013 - 10:21 AM

You're taking a scientific approach, Josh!  Good troubleshooting and observations.  Sounds like a new TPS was necessary, and you're in the ballpark on its configuration. 

 

There were many overlapping issues here, and you have done a terrific job of working through the maze.   Your experience is a gem for others.  Started with a dirty fuel tank and displaced sock, many replacement parts thrown into the mix along the way, plus problems that crossed paths and caused real confusion.  You inherited a "nightmare" by some estimations, I think this is all worthwhile in the long run, as you'll end up with a much more reliable and predictable Jeep Wrangler.  You're now replacing defective parts without "guesswork", and this is way up the learning curve.

 

Your engine's current running condition sounds much easier to troubleshoot, Josh. You may have a clogged fuel filter at this point, and the dripping injector is a concern.  I'm confident that you'll nail it this round.  I'm still of the opinion that a fuel pressure/volume check at the inlet to the TBI would be useful.  Your Harbor Freight tester idea makes perfect sense, you don't plan to use the tool day in and day out, so this would be the right approach for the current project.

 

We haven't discussed the TBI pressure regulator setting.  This is adjustable, and I have provided the steps in the PDF below...The test and adjust does require a pressure tester, so again, the Harbor Freight kit makes sense.

 

You want the right fuel pump pressure and volume of fuel flow.  You want the correct regulator pressure setting (14-15 PSI tested at the TBI regulator test port shown in the PDF.)  The injector needs to flow fuel on closed loop commands.  The cold start/warm-up enrichment needs to work, the system needs to drop into closed loop at the right stage...If the fuel filter is clogged, you might get sufficient pressure without volume, so volume is important, too. 

 

On that note, you would be able to check volume more safely at the regulator test port, as the pressure is much less than the fuel pump supply pressure.  Be careful here, this is gasoline!  A "T" into a large coffee can or gas can could be helpful, with key on/engine off during the test.  Set regulator pressure before checking volume flow.  Adjusting the regulator pressure might solve the fuel drip from the injector.

 

Attached File  2.5L TBI Pressure Settings.pdf   894.98KB   23 downloads

 

Thanks for having the patience to push through on this—especially in an apartment workspace!  If you had sublet the project to a shop, you'd be unsure of the long-term prognosis and would be out a good deal of money by now.  By fixing this yourself, you are very aware of 2.5L TBI troubleshooting, and others are benefitting from your experience and gained knowledge!  I'm sure they are appreciative of your efforts, findings and strategies...

 

As a footnote, Josh, if you find that the inlet fuel pump pressure is too high for the regulator's range, there are inline fuel pressure regulators available from Summit Racing and others to drop down the incoming pressure—without restricting flow. 

 

Another concern with the TBI system is the return line to the tank.  If the return line is pinched, clogged, kinked or otherwise restricted, the fuel pressure at the regulator and port will soar.  If you have normal inlet pump pressure and very high test port pressure that cannot be dropped by adjustment of the regulator, suspect a restriction or obstruction in the TBI return line to the fuel tank. Check hose routings!

 

On your TBI system, the pump pressure goes directly to the TBI pressure regulator, and the TBI regulator has to buffer whatever incoming pressure exists.  Incoming pressure, therefore, is very important, and we discussed the pressure range for the pump earlier.  Test to confirm...

 

Moses



#50 Stinger87

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Posted 04 December 2013 - 03:23 PM

Yeah I think tomorrow after work I will go ahead and get the set to add to my tools. I was reading the PDF file you attached and the only thing is my regulator does not have a screw to adjust the pressure. Maybe it is old and got sheared off. I will keep you posted again tomorrow hopefully with some pressure readings that I am getting. Sometime this week I'm going to inspect the timing again since I've made a lot of changes to the electrical side. Thanks again for all the help so far Moses you are filled with knowledge and I appreciate you taking time out of your day to help.

#51 Moses Ludel

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Posted 04 December 2013 - 08:30 PM

Pleased to add comments and assist...Checking the timing by the factory method might help, it's electronically controlled, so follow the official Mopar procedure for setting the base timing.  Good you're getting the pressure testing equipment, you'll demystify the regulator and other issues, Josh, and Harbor Freight seems like the cost-effective tool source in this case...

 

The source for the PDF on the TBI adjustment is a 1989 Mopar Service Manual for Jeep.  Should be reasonably accurate on all counts.  Check under the regulator bowl for signs of an adjuster screw, a mirror might help.  If possible, avoid the need to unbolt the TBI unit again.

 

Moses



#52 Stinger87

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Posted 08 December 2013 - 08:13 PM

Good evening I hope everyone had a good weekend. haven't done anything with the jeep this weekend waiting to get a line made tomorrow so I can have a leak free fuel pressure tester for the jeep. Once I get it I'll get some readings and post some pics just wanted to give a heads up and that I didn't give up on it yet haha.

#53 Moses Ludel

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Posted 09 December 2013 - 11:09 AM

Thanks for checking in, Josh...Please upload some pics of the pressure test (800 pixel width photos work nicely), many 2.5L Jeep folks will benefit.  Thanks for following through on this troubleshooting step, you won't regret it, the info will be conclusive!

 

Moses



#54 Stinger87

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Posted 09 December 2013 - 03:04 PM

ok so here is what i got so far. I got a line made for the fuel pressure tester to hook right up to my tbi unit but it appears that i have a faulty gauge. I know i have a good amount of pressure to the gauge because when i disconnect the gauge and turn the key fuel shot about 4-5ft. I shouldn't be shooting fuel everywhere but working solo and having to reach in turn the key while keeping an eye out for pressure this seemed to be the only way. Anyway the jeep does fire right up but the spray pattern coming out of the injector now is horrible. I'm going to check to see if i can take it apart and clean it and if not ill just get a new one because it looks to be clogged with contamination from the tank.  I have two picks of how i set up the fuel pressure line if anyone needs more pictures i can grab more.

Attached Files



#55 Moses Ludel

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Posted 09 December 2013 - 09:23 PM

Josh, is this gauge hooked up to the return line to the fuel tank?  If so, the effect is like a kink or obstruction in the return line: The gauge is a stopping point with no "T" back to the tank.  You do not want to check pressure on the return line, regardless.  The pressure check is at the small port plug opening (threads into the TBI unit) shown in the factory shop manual PDF illustration I supplied earlier.  Locate the test port and removable plug in the PDF picture.  Zoom into the PDF, this can be done in Acrobat or Adobe Reader, simply pull into the illustration to get a better view of the test port location. 

 

Also note in the factory manual that it says a restriction in the return line will cause the pressure to spike very high, which may be what you're experiencing at the gauge.  The test port pressure, by comparison, will only reflect the regulated pressure at the TBI unit (if correct, 14-15 PSI). The fuel supply and return lines would be independent of the test port pressure.

 

To test incoming pressure to the TBI from the tank, make a "T" for the inlet pipe connection.  The gauge becomes one leg of the "T", the other two legs would be the fuel flowing from the pump into the TBI unit.  This should be actual, unregulated fuel pump pressure.  Again, do not restrict or attempt to test pressure on the return line, this line must be unrestricted all the way into the fuel tank.

 

Let us know what you discover...

 

Moses



#56 Stinger87

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Posted 10 December 2013 - 05:49 AM

In my picture i have a bass fitting connected into the test port near the return line thats the only reason it looks slightly different. From what i can tell i have it set up exactly how the books pictures for a TBI engine has it set up. It looks like a fuel line but its just the brass fitting i used in the test port to hook up my gauge. I then ran a line to my gauge from that port. I turned the key on heard the fuel pump turn on but the gauge had 0 on the reading. That is when i removed the gauge and hit the key to make sure pressure was getting to it and a powerful line of fuel shot out. I also took the gauge to work and used our shops fuel pressure set and hooked it up to a MPI engine and it still had zero psi. im going to see about borrowing a gauge from work or purchasing another one.

 

This here is kind of getting ahead of myself but on the bowl that the fuel pressure regulator and spring sit in, at one time it did have the adjuster screw in it but looks like someone cut and ground it off so no more adjustments are able to be made if need be. With that being said any ideas on where to get a new one because i cannot find a part number and i hope i wouldnt have to buy a new unit.



#57 Stinger87

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Posted 10 December 2013 - 07:13 AM

ok new discovery, my gauge does work. Now that i know my gauge is working that leads me to think the jeep's fuel pressure is pretty much at zero. Yes the pump is pushing fuel but i am thinking it has to do with the regulator and that small spring that i installed. What i will do is reintall that old spring that was larger and then check my fuel pressure. Earlier i was saying that the large spring was causing too much pressure but i need to be able to get some sort of reading. If my pressure is too high i should be able to either find a new spring or get an inline regulator. I am not 100% on all of this but it sounds like a good direction to go in. My symptoms right now sound directly to being a fuel problem. Idles good with the fuel its getting but once you put a load on it and accelerate it doesn't have enough fuel to compensate for the amount of air coming in.

 

Currently we are in the middle of a rain/snow storm so hopefully i will have some more updates soon.



#58 Moses Ludel

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Posted 10 December 2013 - 10:42 AM

Exciting development, the pressure gauge is telling us something!  Interesting that the fuel shot out of the port but the gauge reads zero.  Something is "bleeding off" the pressure or there is no "column" of fuel in the system.  This could be a mechanical issue with the fuel regulation and/or passageways, either not adjusting pressure properly or bleeding fuel off and redirecting it to the tank.  The latter would explain why there is fuel spurting from the port but no pressure. 

 

The regulator must hold the pressure at the TBI unit, enough pressure and volume to provide a continuous, 14-15 PSI flow of fuel to the engine.  By design, any excess pressure/volume simply redirects to the return line.  When not restricted, the return line is an immediate bleed.  The return line has no backpressure, and the fuel simply runs back into the tank.

 

You're on the right track.  Either the fuel gets rerouted when the plug is in place (pressure builds) or there is no pressure, as you suspect.  I would still take a quick read on the pressure line coming into the TBI from the fuel pump to establish a baseline/reading for the fuel supply pressure.  I would check the supply pressure two ways: 1) connect the line directly to the gauge, bypassing the TBI unit altogether, and 2) make a "T" into the TBI and to the gauge.  If #1 is a success story (showing a nice, continual pressure reading on spec) but #2 is not (pressure drops when fuel moves into the TBI unit), then the pressure regulator is defective and returning all fuel to the return line, which drops the fuel pressure to "0".  If that is the case, there's not enough fuel to run the engine...Make sense?

 

If the incoming fuel pressure by itself (#1 test) is erratic, there's something preventing tank fuel from reaching the TBI unit under pressure.  This could be a pressure or supply problem (unlikely the pump, as you installed a new fuel pump that presumably works well) or an obstruction in the fuel supply between the pickup point for the fuel pump and the TBI unit.  A restriction could be anything from a clogged fuel filter to a kink or packed debris in the supply line, a clogged pickup in the tank, or even a vacuum/tank pressure issue caused by the evaporative emission system (unlikely but possible if someone has tampered with the EVAP hoses or there is a defective EVAP canister).  You've ruled out a lot of these possibilities, they're still worth mentioning. 

 

     Note: EVAP system issues were highly prevalent with carbureted engines and their low fuel pump pressures; however, this is near impossible with high volume/pressure submersible fuel pumps. Normally, I would not suspect the EVAP on a TBI system and would take that system into account only if you cannot pass an emission tailpipe test or if you smell gas fumes with the engine shut off.

 

Restricted fuel flow will not impact pressure, but it will get a "0" reading if no fuel is moving into the fuel gauge.  Again, you need both pressure and fuel volume from the tank to the TBI

 

This is all very taxing when working outside in freezing weather, that's why the pressure tests help so much.  You can more quickly isolate the trouble area.  Josh, you'll be an "expert" on 2.5L TBI before this is over, and your Jeep will be reliable and predictable.  Sorry that you have to perform this work in the freezing weather...

 

Moses



#59 Stinger87

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Posted 11 December 2013 - 02:46 PM

Today I didn't do a whole lot with the jeep but I yanked the tbi off the top of the motor to thoroughly clean and go through it. I'm going to replace the 4 vacuum lines on it and inspect all the ports to make sure they are free of contamination. I am also curious if there are torque specs for the brace that holds down the injector and for the three screws that hold the regulator bowl in place. Other than that once I get the new injector o rings and vacuum lines and install the factory regulator spring I will be testing for pressure again. I should have another update come Saturday.

#60 Moses Ludel

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Posted 12 December 2013 - 11:45 PM

Josh...Factory manual refers to the injector brace ("retainer") screws as "tighten retainer screws". Similarly the 3 regulator bowl screws are "tighten screws".  No torque specs, use good judgment, these screws should be securely tightened without stripping threads on the screws or pot-metal TBI parts.  Do not over-tighten and warp parts, either. A good grip on a screwdriver with a good tip, make the screws very "snug"...Make sense? TBI to manifold mounting nuts are 16 ft.-lbs.

 

I'm looking forward to accurate fuel pressure readings. Not sure what you want to do about the regulator adjuster screw. You may need to "make" an adjuster screw. If so, Fastenal and others have high tensile screws with allen heads. (Lowe's has even been known to provide some of these, at least Grade 5 U.S. or Metric 8.)

 

If you can find the right length adjuster screw and access the allen head with a hex allen wrench, that would work. Be very careful removing the sawed off adjuster screw. If you strip the threads of the regulator bowl bottom, you'll be looking for a bowl. Also, make note of any seal here, if the design calls for fuel around the screw, make sure you take that into account and seal it properly. 

 

To save time in the cold weather, here is one more PDF of service procedures. Make certain that all of the parts in the diagrams are present in your TBI unit when you take it apart. Zoom into the illustrations for details. This will help prevent overlooking missing parts:

 

Attached File  2.5L TBI Service.pdf   151.56KB   10 downloads

 

Moses

 

 

 

 

 

 



#61 Stinger87

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Posted 14 December 2013 - 11:46 AM

Finally got a fuel reading and almost positive on why my emissions levels were horrible (excessive Fuel pressure). On top of that i got my new vacuum lines installed, new injector and orings (injector no longer drips with key on engine off) . For my PSI readings i had aprox 16-17 psi which is too high. I need to be around 14-15. The weather here is terrible right now so i didnt check for kinked or blocked return lines. Tomorrow it should be decent out just cold so i will check to see if there are any messed up return lines. Worst case scenario would be having to remove the bowl from the TBI and drilling out the old adjuster screw. That wouldn't be too terrible i could take it into work and i have all the tools there to make it an easy job. I did not drive the jeep but i am pretty sure that the jerking/ bucking is gone. It was bucking i believe because my fuel pressure was around 1 psi. Ill do another post hopefully tomorrow to let you know if my fuel return line is messed up.



#62 Stinger87

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Posted 14 December 2013 - 11:56 AM

oh yeah i forgot to add that i re-installed the factory spring. The spring was in the picture i posted a while back but it was the huge spring. So for future reference for someone that has to do a fuel pressure regulator on this don't use the one that the parts store supplies with the regulator unless you know for sure you can adjust your regulator to the appropriate specs. Again the spring supplied from the store was about 15 psi too low compared to the factory one.



#63 Moses Ludel

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Posted 15 December 2013 - 07:49 AM

This sounds promising.  16-17 PSI would likely run okay, though a bit on the high side as you share.  If you can drop it to 14-15 PSI, all the better!  You've worked your way through a lot of "stuff".  The regulator spring findings and return to the heavier spring should be a big help and insight for others.  The use of the pressure gauge tester, in the long run, is a real money saver.  It narrowed down your trouble spots.

 

Good to check the return flow to the tank, just as a precautionary.  Vacuum line renewal can make subtle differences in tune and performance with EFI...

 

You're closing the gap, Josh...Weather permitting, you'll have a reliable Jeep shortly.  This exchange should prove helpful to many other Jeep Wrangler and XJ Cherokee/MJ Comanche owners with pre-1991 2.5L models!

 

Waiting for the good news...

 

Moses



#64 Stinger87

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Posted 15 December 2013 - 08:16 AM

The jeep does run pretty good at 16-17 psi but I can feel the sputter a little bit at low rpms. I've already done so much work to it in not going to settle until it is running 100%. Tomorrow I am going to use a drill press to make a small hold in the current adjuster screw then use a bolt extracter to remove it. I want to install my own adjuster screw to set the pressure exactly where I want it. The thread pattern looks very course and might be hard to find a bolt with the exact match. Also the return line looks like it is free of restriction but I may go ahead and replace it with a fresh line. Future reference for my next fuel pump I do on it I will probably make it common practice to change that line due to the fact you have to just about drop the tank to get to it. I'm going to check eBay real quick to see if I can find any used or new bowls for sale.



#65 Stinger87

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Posted 15 December 2013 - 08:35 AM

Alright so i found a company that sells just about everything you need for the tbi engine on the jeep. They have kits for the regulator, spring, bowl and screws for $30 which is almost half the price of the regulator from napa alone. Anyway the company is called Motor Man Fuel Injection. I am going to give them a call tomorrow to see if their bowl has the adjuster screw or not. Ill post back again tomorrow about this. Here is the ebay link i found

 

http://www.ebay.com/...9e00edf&vxp=mtr



#66 Moses Ludel

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Posted 15 December 2013 - 11:39 AM

Very helpful to 2.5L TBI Jeep owners, Josh!  If you do end up "restoring" the regulator screw, make note of what keeps the screw from backing out.  It may be regulator spring pressure...I have a safeguard idea: Consider placing a lock nut on the screw, outboard of the bowl.  Once you adjust pressure to spec, you can tighten that nut to assure that the screw will not back off. 

 

Also, just another idea:  Consider use a copper sealing washer between the lock nut and bowl if there is fuel in the bowl.  This will provide the "leak proof seal" you need.  There should be a copper washer available with the correct I.D. for your bowl adjuster screw...

 

Moses



#67 Stinger87

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Posted 16 December 2013 - 08:06 AM

Just made a purchase from Motor Man fuel injection and customer service was excellent. Quick easy and friendly transaction. The gentleman that i spoke with told me that my spring in my regulator bowl was faulty. With his set up, the new fuel bowl and spring will provide the correct PSI needed to run the jeep at factory specs. I told him mine has a broken off adjuster screw and he said it sounds like someone has tampered with it in the past. Maybe maybe not. I will have the parts by thursday so hopefully after work i can install those and get another reading. If my reading does not change i may try another gauge to ensure mine is reading the correct pressure. If both gauges compare then i will go back to looking at my return line. The return line will be the last part of the project that could cause my fuel pressure to be slightly off.

 

Crank Position Sensor- is there anyway way of testing this sensor. I know i can check for ohms but i do not know what the factory specs are.



#68 Moses Ludel

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Posted 16 December 2013 - 08:50 AM

A new bowl and spring should do it, Josh! The cut off screw will be visible when you remove the old bowl, this could actually be "California emissions" or some other tamper-proof mandate, maybe a hasty factory method for making sure the adjuster is not cranked up to increase fuel flow or whatever.  Long shot guess.  Curious: Is the Jeep a "California Emissions/EPA" vehicle?

 

The CPS test is across the "A" and "B" terminals (labeled on the sensor connector) with the sensor unplugged.  You're looking for 200 +/- 75 ohms, a fairly wide variance.  The test calls for "engine hot" during the test, so without giving yourself a nice burn, carefully unplug the connector after engine shutdown.  If you have gloves that still offer dexterity, use them.

 

Moses



#69 Stinger87

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Posted 16 December 2013 - 09:58 AM

I will check when i get home to see if it is california emissions which i do not think it is. Secondly on the Crank position Sensor if i take it out to clean it do you know if it came with a factory spacer to set up the correct positioning of the sensor or is it just plug and play on this model. I know some of the crank position sensors i deal with will have a small spacers on the end of the sensor and once you crank the engine over it removes the spacer. I am pretty sure this one is plug and play just checking before i mess with it. Again thanks for all the help this far! I think i can finally see light at the end of the tunnel



#70 Moses Ludel

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Posted 16 December 2013 - 10:42 AM

Should be plug and play, Josh.  At any rate, having been in the housing forever, it should come out and go back into position the same way.  The biggest issue with these durable sensors (which generally either work or they don't) is contamination by oil and grease or grit from the engine and road. 

 

The tin ware needs to be in place at the bellhousing to keep debris out.  What often goes on with sensor trouble is oil contamination caused by a leaking rear main seal on the engine.

 

Light at the end of a tunnel...and it isn't an oncoming train!

 

Moses


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#71 Moses Ludel

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Posted 19 December 2013 - 12:59 AM

Josh, I'm curious about Motor Man and the regulator parts, as finding these parts is unusual.  Most of the 2.5L TBI pieces are not available from Mopar any longer.  The cohort of Jeep engines that use Renix TBI would be 1986-90 XJ Cherokee 2.5L and '87-'90 Jeep Wrangler YJ 2.5L fours.  I'm wondering what/where Motor Man pieces come from, whether they are NOS Jeep/Mopar or another source?  Let us know. 

 

Below is a 1987 YJ Wrangler engine block (side view) for those unfamiliar with this engine.  For detailed information on tuning and troubleshooting a 2.5L TBI four, see my 2.5L four 'how-to' article coverage at the magazine with a full set of photo illustrations:

 

Attached File  Stroker Oil Filtration (3).jpg   129.87KB   0 downloads

 

Moses



#72 Stinger87

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Posted 19 December 2013 - 02:20 PM

I just received my parts and they look exactly like the factory ones. I am not sure where they get them from but they look legit. The spring is large like the original one and even the regulator looks the same too. The other regulators had minor discrepancies when compared to the original but this one is spot on. I'll have more time Saturday to do everything to it and get back to you.

#73 Moses Ludel

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Posted 19 December 2013 - 04:17 PM

Good news!  Sounds like parts that will work and replicate the OEM pieces...You now have an adjustable regulator—and the pressure tester to verify spot-on 14-15 PSI fuel regulation at the TBI unit!

 

Did you take your tester to work and check the accuracy of the Harbor Freight fuel pressure gauge?  Probably a good safeguard as you set the new regulator bowl's adjuster screw.  I doubt whether they can "pre-set" these adjusters to exact pressure.  Let us know how close the adjuster is "out of the box".  I would guess that you'll be setting the pressure adjustment...

 

Moses



#74 Stinger87

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Posted 21 December 2013 - 11:44 AM

Today i installed the new spring, new regulator and new fuel bowl. The parts that i got actually looked like the original (bad) parts that i first took out. Definitely go with Motor Man parts over auto zone, rock auto, Napa etc. These guys have quality parts that work excellent.

 

I hooked my TBI up and used the fuel pressure tester and fired up the jeep. The jeep instantly turned over and idled perfectly and quiet. The psi reading was exactly 15psi and did not bounce at all just a steady and solid 15. I noticed that i still had a minor sputter so i checked my tps voltage and everything was still with in specs. The second thing i did was to see if i still had a sputter if i disconnect the hose from the EGR valve and my sputter instantly cleared up. As of right now i have the EGR disconnected because it runs great without it.

 

I then took it for a ride and it is running perfect i have zero complaints about it. I had good power through all gears feels about what a 4 cylinder should have. I believe i shouldn't have any more issues with the fuel system/engine for a good while. I am going to run it all weekend and week to see if everything holds up and i will get back to you for hopefully a final post in this thread. 

 

Attached File  15PSI.JPG   163.03KB   1 downloads Here is my gauge hooked up after i re installed the new spring and new regulator and also the new bowl.

 

Attached File  New and Old regulator.JPG   188.09KB   0 downloads Here you can see the difference in the regulators. The one on the left is from Motor Man which looks exactly like the original. The one on the right is the same ones that rock auto, Napa etc will supply. I feel if the regulator on the left was good enough for Jeep to use then its good enough for me and that's the one that i used.

 

Attached File  New and Old Spring.JPG   158.79KB   0 downloads Here i have my two springs, the one on the left is the original i believe from 1989 and the one on the right is from Motor Man. It's a small difference but you can clearly see the original is slightly worn out. The one or the right is about 1/8" taller then the original. With that small of a difference it changed my fuel pressure from 16-17 to 15 psi and now my jeep runs perfect. Also, like Moses said, this proves how important the correct fuel pressure is. 

 

I had a lot wrong with my jeep and now i feel i can finally close this chapter and finally enjoy driving my jeep around and now have some money for other add-ons for it!



#75 Moses Ludel

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Posted 22 December 2013 - 12:13 AM

Josh, this is great news.  You rode it out, learned a bunch and solved your Jeep's problems!  Motor Man looks like quality, OE type parts. 

 

As for the EGR, check your vacuum hoses. The EGR should not open at an idle, as it uses a "ported" vacuum source.  Ported, like with a carburetor, means vacuum sourced from above the throttle valve.  Ported vacuum will be near zero at a closed throttle, then pick up immediately as the throttle opens, then drop to nearly nothing at wider throttle openings.

 

The EGR actually has a positive function in addition to lowering NOx for tailpipe emissions requirements.  The EGR cools the upper cylinders from as high as 4800-degrees F to below 2500-degrees F for NOx reduction.  This dramatically reduces risk of detonation/ping and upper cylinder fatigue.

 

If your EGR does not seat completely, that could be a defective or clogged valve.  From what you describe, though, the EGR does work fine with vacuum removed.  When your vacuum hoses are correctly hooked up, you will have close to zero vacuum applied to the EGR when the throttle is closed (idle) and ported vacuum is very low.  Identify a ported vacuum source for the EGR.

 

Congratulations, Josh!

 

Moses



#76 Stinger87

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Posted 22 December 2013 - 06:30 AM

I traced all of my vacuum lines and they match to my haynes manual. The only thing i guess that could be faulty is the purge solenoid. Ill check to see if i can find some tests to perform on it.



#77 Moses Ludel

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Posted 22 December 2013 - 09:44 AM

Josh, there's a simple test for the vacuum issue.  Hook up a vacuum gauge to the EGR line (a "T" if you prefer testing real time performance).  Measure the available vacuum to the EGR valve with the engine idling, throttle closed.  Open the throttle and watch the vacuum change.  Note where the EGR valve opens in terms of engine-supplied vacuum.  Keep in mind that EGR is often routed through a thermal vacuum switch to prevent EGR function when the engine is cold.  You may need to perform this test with the engine cold and also warmed up.

 

Additionally, you can hook a vacuum gauge/hand pump to the EGR valve itself. With the engine idling, apply vacuum to the EGR valve and see if you notice the same "roughness" that you've experienced when the vacuum supply line is hooked up.  This will be your true test of both the EGR valve and the trouble symptom or roughness you experienced.

 

Here are details on testing the EGR system outside of the EGR valve itself:

 

Attached File  2.5L TBI EGR Testing.pdf   90.4KB   8 downloads

 

Your Jeep is now far more reliable, and you're well prepared for backcountry use.  It's very important with a Jeep 4x4, or any other 4x4, to have a dependable and predictable powertrain.  Off-pavement, you'll need that highly stable idle, immediate response on throttle tip-in and performance on demand...You're now a troubleshooting "expert" on Jeep 2.5L TBI, which should make you popular in early Jeep 2.5L TBI circles...

 

You did it, Josh!

 

Moses



#78 Adam F

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Posted 15 April 2014 - 01:05 PM

So, I've been following this, and it seems I've been having similar problems with my 89 2.5 TBI, but a little worse.  My Jeep was running OK, high idle, and small misfire here and there but runs OK for the most part.  One day went to start and it was spitting and sputtering, barely ran unless I revved it way up.  Seems a large amount of fuel is being sprayed by the injector.  I can pull the connector off the injector and it smooths out for a few seconds before it dies.

 

 I pulled the regulator and it looked ok, spring was springy, diaphragm was not ripped.  Going to do a pressure test tonight.

 

What ended up being the problem?  The regulator?



#79 Adam F

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Posted 16 April 2014 - 08:10 AM

So, I ran a pressure test.  Soon as I fired it up, it ran fine.  Pressure was 14-15psi.

 

What's up with that? 



#80 Stinger87

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Posted 19 April 2014 - 12:28 PM

Adam f yes my overall issue was my fuel pressure regulator. On top of that the spring was worn out too. I had a few other issues such as a partially clogged fuel pump because the sock fell off the pump somehow. I'm guessing it wasn't properly installed.

 

Since I had that issue, I changed the fuel filter then I realized that gunk made it into my injector and was keeping it open. So after the spring and regulator pump filter and injector, it ran like it should. Currently I still have a slightly rough idle once my jeep gets warm but I have zero performance issues now. Let me know if this helps, and if not, we can try something else.



#81 Stinger87

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Posted 19 April 2014 - 12:37 PM

Little Dana 35 doing work at 180000 milesAttached File  20140419_111834.jpg   267.05KB   0 downloads

#82 Adam F

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Posted 21 April 2014 - 10:05 AM

I ran the jeep again, and its back to running like crap.  Idled OK but when I took it for a test drive, it fell on its face.  Would barely go around the block, falls on its face at anything above idle. Pressure is now 12-13psi.  Died just before I could get it back in the driveway.  Wouldnt restart, gauge shows no fuel pressure.  Sit for a while and it re-fires.  No fuel pressure while cranking.  Is this due to the O2 sensor being flooded out?  I crank crank crank, let off and go check the gauge, nothing. Should there be fuel pressure while cranking? I read that its only when the fuel pump is running.  Does it bleed off that fast, from when I'm cranking to when I go check the gauge?

 

Going to check a few sensors and see whats going on, and check to see if I'm loosing spark when it dies.

 

One more day of testing before I give up on it for the season and focus on my boat.



#83 Moses Ludel

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Posted 21 April 2014 - 11:35 AM

Adam F...Pressure is either bleeding off or you simply do not have sufficient fuel supply to the TBI unit.  My test at this point would be a "T" on your pressure gauge kit with a fuel hose or pipe running to a safe fuel container.  Turn on the key (without cranking or starting the engine) and note the fuel flow into the container when the pump is running.  This indicates fuel flow volume, not just pressure, and you need both. 

 

Note: For the engine to idle, you need a shut-off valve on the drain port of the "T" to adjust enough fuel pressure and volume for the engine to idle.  Unrestricted flow at the drain hose or pipe could create too much of a pressure drop, in which case the TBI unit would starve for fuel.  For measuring the fuel flow while cycling the fuel pump without the engine running, you want a drain hose or pipe with the same I.D. as the supply line from the tank to the TBI unit.  The shut-off valve at the "T" is a safety backup during your tests and also serves as a means for restricting and regulating the bleed-off rate as necessary.

 

You may need someone to cycle the key-on and trigger the cranking mode while you watch the fuel flow and pressure.  Sounds awkward to keep jumping out of the Jeep to see what's going on.  Be careful with the gasoline flow into the safe container, gasoline is highly flammable and must be kept away from heat and sparks!

 

One diagnostic tool that works surprisingly well with TBI units is a simple timing light hooked up to #1 cylinder's spark lead.  Since your engine will idle (thankfully!), you can check the fuel flow spray pattern readily.  Timing light hooked up, aim the light at the discharge nozzle of the injector with the engine idling.  You should see a uniform fuel spray cone pattern if the fuel flow is adequate and unrestricted.

 

Since idle seems okay and tip-in under load becomes an issue, try accelerating the engine at a steady rpm increase that might bring about the stumble.  Watch the fuel spray pattern as this happens, and notice whether the spray diminishes simultaneously with a pressure drop on your fuel pressure gauge.  This can pinpoint a lack of fuel flow in relationship to fuel pressure.

 

I'm hinting that the fuel flow may be restricted or erratic as Stinger87 encountered with the fuel filter and tank sock issue.  The in-tank pump's pressure, the fuel flow volume (involving the tank sock, fuel filter, a pinched or restricted supply line and similar concerns), pressure into the TBI regulator and the regulated pressure, plus the actual injector flow, are each important.  You're right about the O2 sensor playing a part in all of this, with the typical trouble symptom being an engine operating in limp mode.  A "bad" or contaminated O2 sensor can wreak havoc.  An EGR issue (valve plunger not seating, an EGR valve stuck open or closed, etc.) can also cause this kind of erratic engine behavior.

 

I heartily recommend not "borrowing trouble".  Simplify by going back to the original malfunction symptom and focus on its possible causes.  Needless parts replacement and experimentation often solve little, this can be costly, and it leaves the solution to chance.

 

Let us know how this troubleshooting unfolds...

 

Moses



#84 Adam F

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Posted 21 April 2014 - 03:11 PM

Thanks!  Problem is though, she will NOT idle.  Have to give it 1/4 to 1/2 throttle or else she stalls.  Even then she is stumbling pretty good.  A little bit of black smoke puffing out the exhaust, with a light black coating on the ground.  Look into the TB while its running, and it seems as if the injector is 
"spitting" short bursts of fuel instead of a fine mist.  This can be heard as well as seen.  

 

I tested the crank sensor, 212 ohms.  Good.

 

MAT sensor - 1200 ohms.  Good according to the chart (tested when the engine (and myself) had cooled off.

CTS sensor - 1200 ohms as well.  

 

Havent checked the MAP sensor yet, as I cant get it to idle.

 

Havent checked the TPS either.  

 

I will have to make a test rig for the fuel flow as you suggested.  

 

What size is the return line on this?  I need to pick up a length of hose and a ball valve to do this test.

 

Also, should I try to use shop air to blow down the fuel lines back into the tank to clear any restrictions?

 

I'm ready to give up on this thing and focus on my boat. I hope I can get her going, I just want a little fun in the sun. Sorry for the hijack, should I start a new thread? 



#85 Moses Ludel

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Posted 22 April 2014 - 08:09 AM

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



#86 Adam F

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Posted 22 April 2014 - 03:07 PM

No check engine light, but I think the bulb could be burnt out because the light never comes on, and other bulbs are out.

I pulled the crank sensor and it didn't look bad, but I went ahead and cleaned it. Fired it up and it idled ok. (Cold start) test drove and it began falling on its face. 1/2 mile drive and it stalled like it did last time. Took about 10 seconds of cranking before it restarted. Idles ok but falls on its face with throttle. While idling, pressure at test port reads 11 to 12 but drops to 5 or 6 when you rev it up. Heres a vid

Fuel pressure drop:

Attempted to check pressure at the feed line direct to pump, but I dont have the right fittings.

Another day……



#87 Moses Ludel

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Posted 23 April 2014 - 08:31 AM

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



#88 Adam F

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Posted 23 April 2014 - 08:48 AM

Thanks Moses.  That's my next step.  Gotta get some fittings first. 

 

I'm going to say I have a failing fuel pump.  Cold, it starts and idles good, and I can lightly feather the throttle and it drives OK.  After a block or 2 down the road, it begins to fall on its face.  Circle back around the block and it stalls.  Seems like the fuel pump cutting out.

 

I probably killed the pump by running it out of fuel a few times.  My gauge is not too accurate, it tends to float around.  (you think this is sender or gauge?)

 

I'll confirm this after I get a chance to find some fittings.



#89 Moses Ludel

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Posted 23 April 2014 - 11:53 AM

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



#90 Adam F

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Posted 23 April 2014 - 04:23 PM

OK.  I got the connections to check the direct pressure from the pump.  Turn the key, and it pumps up to about 25psi.  Gauge leaks a tiny bit, so it may loose a PSI or 2.  

 

I then started it up to warm it up to induce the problems.  Drove it about 1 block, she died, and wouldnt restart like she had before.  With the key on, I now have some rhythmic clicking coming from BOTH the relays on the passenger side near the firewall. (fuel pump relay(s) I assume) and the fuel pump is cycling on and off.  Waited about 15 minutes, tried again, still clicking.  Unhooked battery for 5 minutes, still clicking.  

 

So thats where I'm at.  

 

What would cause the relays to click on and off continuously?  

 

Here's a vid of the clicking 

 



#91 Adam F

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Posted 23 April 2014 - 04:28 PM

Could it be a problem in the ECU?  I've read this link

 

http://www.jeepforum...ors-ecu-492597/

 

But thats for a MPFI setup, not TBI, so I'm assuming the ECU is different?  



#92 Adam F

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Posted 23 April 2014 - 05:43 PM

I let it sit for about an hour, and the clicking is gone, and it restarts.  Let it run for a few minutes, and it dies, and the clicking comes back.

 

So, I've began to remove the ECU to check it out.  I got the glove box and grab handle out, but I can't figure out how to get the ECU unbolted.  

 

HELP!



#93 Moses Ludel

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Posted 23 April 2014 - 06:11 PM

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
 
 
 
 
 
 
 
 
 
 
 
 
 
 



#94 Adam F

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Posted 23 April 2014 - 06:28 PM

The ecu is behind the glove box, and I can access 2 of the 3 screws, im having trouble getting at the 3rd one. There has to be something im missing… .

#95 Moses Ludel

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Posted 24 April 2014 - 09:45 AM

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



#96 Adam F

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Posted 24 April 2014 - 10:17 AM

Thanks!  The relays are the same exact type, and I did switch them with no luck.  They are BOTH clicking with a perfect rythm, one clicks then the other clicks.  Pull one, the other still clicks, vice versa. 

 

I will check and clean all the grounds.

 

Did you read my link I posted above about the capacitors  being burnt out on the later style MPFI computers? 



#97 Adam F

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Posted 25 April 2014 - 02:35 PM

Found 1 ground disconnected and 1 loose at the firewall. Reconnected and it runs great! Thank you moses for all your help! Now I can move on to installing power steering!

#98 Moses Ludel

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Posted 25 April 2014 - 10:33 PM

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





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