LesMizzell

1996 Cherokee - It's done this three times:

1. Couple months ago, I drove maybe 3 miles to a Starbucks, went in for 5 minutes, came back out, and on restart it was running VERY rough. Eased out of the parking space, pressed the gas ... it shuddered just a bit, backfired, refused to accelerate, and shut off. It immediately started after that, and ran great. I really didn't give this another thought.

2. Approx 4000 miles after #1, I drove approx 100 miles to an airport in another city to pick somebody up. Stopped in the cell phone lot for maybe 10 minutes. On restart, just like the above. It ran rough, I nosed out into traffic, pressed the gas, it shuddered a bit, and turned off. This time, it would NOT restart. Engine would turn over, but wouldn't fire. Ended up calling a tow truck. Maybe 30 minutes later when they got there, the tow driver tried it again for grins and giggles. It started perfectly.

The shop I was referred to couldn't replicate the problem, but told me there was a slight leak in the head-gasket and the rotors looked worn, so they fixed all that, replaced the plugs and cables, and told me "you 'should' be OK now", meaning they weren't 100% sure if anything they did was actually the problem.

3. This weekend, almost 4000 miles of running smoothly after incident #2, my wife is away in another city with the Jeep, drives about 2 miles from her hotel after it's been sitting all night, stops to grab some take-out, and it does it again, and refuses to start for her. She calls me in a panic, I tell her to go back inside the restaurant, calm down, and eat her breakfast, then try it again. 15 minutes later, it starts like a champ, and runs perfect the rest of her trip - another 500 miles.

She drives a LOT, and no longer trusts the thing now. She's convinced it's going to leave her stranded in an undesirable location at some point. I dropped it back at the shop that rebuild it for us this morning (I trust these guys), explained what it was doing, and they don't have any immediate ideas. Anything they could come up with, should be causing the problem a lot more than every few thousand miles. They're running diagnostics on everything as we speak, but unless they can get it to do it for them (unlikely), aren't sure they'll find anything. We may end up just replacing whatever the "best guess" is after diagnostics.

Ideas??

wyattjo

I don't know if yours has the ballast resistor on the drivers fender in the engine bay but my 93 does and it did similar things until I replaced the wiring connectors on it and since then it hasn't happened again... From my understanding that resistor uses some power to keep the fuel pump quieter so if the connectors are bad on it the fuel pump doesn't run and in turn the engine runs until fuel is drained from the lines and dies

LesMizzell

Just got it back from the shop. They are "pretty sure" it's the CPS which they said can slowly fail in "interesting ways", including the problem I was having. So, $60 for the part, little bit more for the labour, and I guess we'll see how the next several thousand miles go.

It does seem to crank with a little more "authority" now, if that makes any sense.

95silverstallion

Mine did this today for the first time. Driving at 55mph and shut off instantly. Didn't spit or sputter, just shut off like I turned the key off. I barely slowed to 45mph and it started right back up on its own. A few miles later it shut off and forced me to the shoulder. First try to restart didn't work. I waited a minute or 2 and it fired right up and drove home fine????

LesMizzell

Well - that wasn't it. After running like a champ, wife just drove 150 miles to a job, got stuck in traffic, and while putting along a 5 miles an hour, it started stuttering again, shut off on her, and doesn't want to restart.

She's still sitting on the side of the road waiting to see if it will start back up while I'm typing this.

Oh lord.....

tjwalker

It sucks to be stuck on the side of the road, but the bright side is that if it doesn't start, then it should be relatively easy to troubleshoot the root cause here.

One thing I didn't see mentioned was the "ignition coil". They can be tested for both primary and secondary resistances with a meter and a manual. They can suffer "thermal" (heat related) intermittent failure when they are starting to fail. Assuming you have never seen a check engine light, I'd certainly test your coil to see if it is out of spec or close to being out of spec.

And obviously if it doesn't start at all, gotta do some basic testing to determine what critical component you are missing. Fuel, spark or both. Knowing that helps narrow down the primary suspects here.

Good luck and keep us posted!

Radi

Probably ran a little hotter crawling in traffic, a coil with heat-related failure would make sense. Blast the thing with a hair dryer to get it good and hot, see if it cuts out. CPS can have heat-related failures too, do you know what brand the shop installed? Hopefully not a cheapie. You can hair-dryer test that too, BTW.

LesMizzell

Yea, this now seems one of the "rules" that causes the problem.

She got a friend to pick her up and take her to her job. I drove the 100 miles to pick her up when she was done. Stopped by the Jeep on the side of the road on the way up ... cranked perfectly, so we droped by again on the way back, it cranked for her too, and it drove the 100 miles back home without a hickup.

Sadly, it's been in the shop for this three times now, and the issue still hasn't been figured out. It's left her stranded twice out of town, plus me once, even if only for a little while to cool off. She now no longer feels it's safe to drive and doesn't trust it enough to take it to another job. Seeing that this is the only vehicle we have at the moment that's (was) reliable, she's definitely wanting to sell it now and get something newer she can depend on.

Don't want to see it go, but I feel its days in our driveway are definitely limited. Even if the shop WERE to find the right thing, she STILL wouldn't trust it enough to drive it at this point.

Yikes - haven't actually had to make car payment in YEARS. Wasn't counting on that again any time soon.

cruiser54

I would put a coil on it and check the connectors at the fuel pump ballast resistor, just cuz. Sometimes you have to throw a part or two at something. I forget what years it was, but the 4.0s had a batch of crappy coils. Made by an Italian company somewhat the equivalent of British Lucas electrical parts. Magnetti Marelli.

BillyBoy

Just had the same issue, although because my jeep is relatively "new to me" I can't say I've had the recurring issue.

I replaced the cps, and btw, it really does matter if it's a cheap knockoff vs oem part. I was still having problems. Wire testing everywhere twice said all was good. It still wasn't getting spark/starting. I had someone crank it while I started jiggling plugs/wires. The harness and plug to the coil was the culprit. Get a paperclip, straighten it out, and start opening your harness connectors, 1 by 1, all over the jeep {any you can find} and dilithium grease the connectors. Be VERY careful to only get the grease in the little holes on the connectors and not the just do the pins. Number 1, if you do the pins, it might squeeze out and all over when you replug the harnesses. Number 2, the grease gets all the way in better. While the plugs are apart, look for a pin or pin receiver that are loose or pushed in, possibly making a bad connection.

The other thing you should do is check out cruiser54's write up on renix ground "refreshing." Bad/rusty grounds can cause a lot of weird issues.

Third, check the wires to the battery. My last jeep ran intermittently, I did everything mentioned, and it still didn't help. I took a razor to the red wire {unconnected, of course} and found the whole wire green and salty. Changing a 30$wire fifed it for good.

Good luck.

Radi

Yikes, with that length of a commute I'd be wanting something easier on gas too if you don't need the 4WD lol.
I'd put money on either a heat-sensitive coil or CPS, particularly if the CPS wasn't a Mopar part. 1/2 hour + hair dryer.... re-create the conditions that led to the failure. Seems the shop isn't doing that, just tossing parts and hoping.
If you can get the coil or CPS to cut the engine when you heat it good and hot- you've found it.
Fix it for <$100 and have a good reliable second car. Otherwise in good shape?
No ballast resistor on a '96.

belvedere

One thing to do when it won't start would be to check for spark. Others have mentioned the coil, or even the new CPS if it's an off-brand, and I think those are good guesses, but I wouldn't rule out the fuel pump, either.

allevolution

You found a great shop. Took me 2 months of my own diagnostics and 2 shops before they could figure that out for me.

In short its always something to do with that crappy CrankPS