Sasquatch711

hi guys. once again I am having a random problem with my '91 cherokee. I have the 4.0L motor. I have been working on/upgrading this jeep continually since December but, ever since it's goten really hot outside I've had a bunch of problems, the first of which led to a full cooling system overhaul($400) OUCH!
now I get a problem where I'll be driving along and the jeep will just die, and then refuses to restart. first thing I did was check for spark. and as this problem has been going on for a while it seems like sometimes I have spark and sometimes not (TODAY WHEN IT REFUSED TO RESTART IT HAD NO SPARK) so, I checked the crank sensor against several others which all tested the exact same as the original(AND SWAPPED IT FOR ANOTHER ONE) but, still it was doing the same thing, checked the fuel pump, wiring etc. heres what I've found Fuel pump, is brand new and IS delivering LOTS of fuel to the fuel rail. wiring to fuel pump seemed to be in great shape as well as the relays so I don't think it's got anything to do with it now but, I believe the old pump was slowly failing (it was over 20yrs. old). and however now that I have a new fuel pump/filter I get a random problem where the jeep will just die. it did it to me today and I was able to verify we had no spark at the plugs or coil. HOWEVER when I came back with my truck to jump start it two hours later(we ran the battery down trying to get it started but, ended up walking home) it fired right up and we drove it home, and it seemed to run great!

HELP!!! what the crap is going on here. crank sensor? Computer? wiring?, bad coil?

my coil is a brand spankin new accel high voltage coil....BTW my engine rarely runs hotter than 210-20 now, and I just upgraded to dual electric fans so I don't believe things are getting too hot.....I dunno.........so frustrated

before we got it started and drove it home i had the wife sit inside and turn the key on/turn the engine over.
with the key on and the coil wire harness unplugged from the coil the harness showed over 12V, but I didn't have my multimeter to test the power to the coil before when it refused to start. I am running out of money here trying to fix this stupid jeep, and I really don't want to get rid of it but, at this point I'm at a loss and tired of getting stuck in 100 degree weather. funny thing is the dumb thing ran great all winter even on the coldest days! thanks guys, Jason

tjwalker

The #1 cause of thermal (heat related) failure on the 4.0 is the crankshaft position sensor. However, if you replaced that with a different one and STILL have an issue only when the engine gets hot, then you can pretty safely eliminate that sensor as a cause.

The #2 cause of thermal fail is the ignition coil. Try a different one. Aftermarket coils fail way more often than the OEM coil. I know your coil is new, but you must rule the coil in or out at this point in your process, as this is a process of elimination.

Good luck and let us know what you find!

Sasquatch711

that was my next step is to go and get my old coil out of storage and change it. you're dead right. it's suspicious that the jeep never did this until I changed the coil to the Accel. hopefully I can get my money back from Summit. I had an MSD ignition do the same thing to me a few years ago in my truck. got us stuck when it was 105 degrees outside, no cell phone, out in the middle of nowhere. finally was able to hook up the stock ignition system and she fired right up............so.........maybe it's the same deal here. I can only hope. I forgot my own cardinal rule because I've been so stressed about this, that is, NEVER TRUST THAT A NEW PART IS GOOD! thanks, I'll let you guys know if changing the coil solves the problem

SupermotoFan

OP,

I had the same problem with my Cherokee.

After a new TPS (only worked for 24 hours), and months of messing around with it, I have figured out what the problem is with my Jeep.

Intermittent short in the wiring just before it goes to the connector to the coil.

My solution was to loosen the ground cable that goes to the block, rotate it slightly as to relieve the tension on the coil signal wire, and retighten.

Works fine for the time being.

Sasquatch711

yeah, I hope it isn't the wiring. I am worried about that . I did change out the coil to today and put the factory coil back in and ran the H@#! outta the thing to get it hot, and took several trips, and so far so good, so, maybe it was a bad coil,who knows. BOO on ACCEL if thats the case. at least Summit is willing to refund me my money as today was the last day of the warranty!! keep your fingers crossed, don't want to get stranded again. I need this Jeep to run right as it's my daily driver............................

tjwalker

I've seen quite a few ACCEL coils puke out early.

A stock 4.0 really doesn't benefit much if at all from these coils; the OEM one performs quite well.

SupermotoFan

You might want to take a look at the leads right before the coil connector. I spotted the fact that they were kind of strained (stretched?), and pulled on them for kicks--started right up.

Sasquatch711

well, seems like so far the coil was the problem. we'll see as time goes on if that solves it! cautiously optimistic.....

94JeepCherokeeMan

Old fuel injected 302 in my ford pickup was doing the same thing and it was the ignition coil

thakmfb

just the other day, had a saturn with 2 accel coils on it and did not start. 1 of the coils **** the bed..best part coils were only a week old.

tjwalker

I'd stay away from ACCEL coils. No advantage for the 4.0. Just marketing claims.

And their reliability is not so hot.

SupermotoFan

I will add that the shop that I took my jeep to (same one that swapped the TPS at the start of this process) installed a new coil (the day after the TPS). The jeep ran fine for three weeks, and then developed the same problem again.

Sasquatch711

yeah, my luck it'll die on the trail next weekend!......... at least we'd know it wasn't the coil now! lol. I did inspect the wiring VERY CAREFULLY and i didn't see any obvious signs of a short, bad ground etc. but, you know how that goes, they can be so illusive even with a multi meter unless you get the sucker in just the right position then it may test as good. have this happen all the time with guitar cords, then you get on stage and suddenly you have a bad cord that tested good previously!
my instinct says it was thermal failure of the coil as it NEVER did this before three months ago when I installed the ACCEL coil, and it would only happen when it was really hot, it'd die, refuse to restart, then if you'd let it cool down for a bit it'd fire right up and run great, until it got hot again.

BTW my TPS is fairly new, as is my IAC valve,crank sensor, map sensor,etc.etc. etc. been trying hard to make this jeep nice on a budget but, sometimes I think the "upgrades" aren't really what they're cracked up to be. sucks about the Accel coils. I ran one in my truck for about ten years and it worked great until I dented it on a rock when I was switching engines! I wasn't going to even attempt to use it after that, just went with an MSD blaster 2. been happy w it, no probs. at all.

I got my money back from Summit Racing though. they even paid to ship the coil back. Imagine that, a company that takes care of their customers!

Sas.