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92 YJ 2.5 Randomly Dies....the may or may not start

2K views 37 replies 6 participants last post by  Que89YJ 
#1 ·
I have read many posts with similar issues but nothing that found a fix for mine. My 2.5 YJ engine just randomly stops running, sometimes when cold, sometimes when hot, often times starts back up but sometimes it stays dead.

I have checked fuel pressure, connections on the under hood fuse panel & relay connections, checked all grounds and added a couple more. Replaced the crank position sensor, complete distributor, coil, plug & wires, ECM/PCM, cap & rotor. When it dies the power is killed to the coil. Fuel pressure stays good when the engine quits. Any ideas would be greatly appreciated. Thanks
 
#3 ·
It does not appear anyone has messed with the harness, I have moved and jiggled every wire I can reach (from top and bottom) when it is running and it changes nothing. I have had it go for 1-2 weeks with no issues, then boom...it dies. It will also have a random quick dead miss and keep going with no more issues.
 
#6 ·
Use the links in my signature and follow the directions for checking codes. When you check power to the coil after it dies you need to check the power with key on and since the ecu supplies ground only when firing a plug you need to measure the voltage referenced to battery negative. Also if you know how to check for spark, look for spark at the plug. Post back the codes, voltage check at the coil, and spark check. we can get you fixed up.
 
#10 ·
4.7 is low. Check voltage on both wires on the coil. One side will be less. Its still low even if it's the other side. The ASD relay feeds the coil, injectors and the alternator. You need to check power at the injectors and the smaller wires at the alternator the same way I think the power wires are green with orange stripe. Also check the power on pin 30 of the ASD relay. Pull it and there is a diagram on the side for the pin numbers.
 
#16 ·
Ive had them cause probs with no codes at all. And its been the issue with more posts than not. I dont have analitical ( dont spell check that ) proof....just a gut feeling!
And more 2.5 CPSW than 4.0's. not sure why that is. Ive seen them fail ( open circut cps code )......fail randomly with no code.....the end lightly rubbing the fly wheel and getting gummed up with metal shavings or mud ( no code ) I acually keep a spare CPS in a drawer JUST for testing a no start or stall problem. First thing i do once i check spark and fuel, is slap a diff cps in the jeep. Dosnt always work, but is does often work. Reciently in Michigan delt with a friend got a flat tire.....towed home....replaced the tire and the jeep was dead. CPS. Why?.......no clue at all, but re installing the cps fixed it. So im not making this bet armed with imperical knowledge......just betting on the odds
 
#19 ·
try loosening the retaining bolt.....raise or lower it a tiny bit.....grease the plug. and/or replace with a spare. I often remove it and look for signs of rubbing on the tip. Ive seen so many head bashing issues be as simple as the cps to many times. Nothing worse than weeks of diognosing electrical only to find out a sensor was being a jerk.....lol
 
#22 ·
I was thinking today, this thread HAS to be driving Que nuts. Were no longer searching to track down the cause by careful step by step diog.....were taking bets on random guesses based on "gut" feelings.
Sorta goes against everything Que is........sorry brother. In the end you'll be right, so just let the kids play....lol
 
#23 ·
Now the jeep is running, pretty hard to track down the issue when it randomly runs, sometimes it will stay idling for an hour or two with no issues. (Que89YJ) What kind of voltage am I looking for at the injectors an small wire at alternator? The ASD #30 has same voltage as battery.
 
#26 ·
OK let's start with observation when it happens again. You said you have fuel pressure and you don't have a code and you had no power at the coil.
Look at these things.

Does the check engine light come on and go off when you cycle the key after the stall. Do you hear the fuel pump cycle when you cycle the key.

Coil voltage checked to battery negative. Same for a couple injectors too. Make sure the key is on.

Post what you get.
 
#28 ·
The check engine light does come on and off as I cycle the key, before and after stalling. The fuel pump cycles with the key, I left the fuel pressure gauge on and it never drops lower than about 45psi running, idling, high rpm or when it stalls. The green feed wire to the coil reads .2v with the key in on position (when it runs)....fluctuates between .09v-7.3v with key in on position (when it does not run). When you unplug the coil feed from the coil it reads same as battery. The green wire reads about 14v while it is running. The injectors get a pulse signal when cranking over even when it is not starting.
 
#29 ·
Ok, your fuel pressure is way high. You should have about 31 psi idle. You have an issue. You should have 31 psi idle, pull the vacuum line off the Fuel pressure regulator and it should go to 39. Hook the line up and turn off the jeep it should stay above 20 psi for longer than 20 minutes. The fuel pressure is not the reason for the stall but definitely effects economy, restart and performance.


Now back to the coil. That voltage is not right. Did you reference the battery negative when you were checking the voltage reading?
 
#31 ·
Mike how often does it stall. You said sometimes it doesn't start right back up but other times it does? When it doesn't want to start right back up you said you still hear the fuel pump and the Check engine light comes on?


Have you tired a relay swap with the asd and horn?
 
#32 ·
Actually swapping relays was one of the first things I tried last fall. I have had it run for a week without stalling and other times I cannot make 15 seconds....just no rhyme or reason. Yesterday when trying to do test it ran for 10-15 minutes and would not stall....today I started it up and pulled up to my garage and it made it 100' and died...there it sits. When I was running it last summer I could occasionally hear/feel a quick miss but it would keep running down the road, sometimes it would die doing 50mph and I would just drop a gear and let it spin the motor until it picked back up. The fuel pump cycles with key and check engine light comes on. Sorry to ramble on but this thing driving me crazy.
 
#35 ·
I am searching for a wiring diagram for my 91 wrangler, 2.5, manual. I have a good base knowledge of the wiring layout but I need to better wrap my head around this to figure out my issue. It seems I am having a voltage issue between the ASD relay and the feed to the coil.
 
#37 ·
Que89yj, I trie to PM you but I did not have enough posts on the forum to qualify for PM's. I did try putting 12 to the coil feed wire, even that would not make it run. I have a video showing the voltage as it is running and dies.....can you PM me your email so I could send it to you? Thanks again for the help.
 
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