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1995 XJ - Dying while driving, no start, then periodic short-lived restart

Blaine B.

NAXJA Forum User
Here's the deal. In mid July I was driving along when all of a sudden the XJ died. I coasted off to a side street and tried to restart, it would not start. Had a buddy tow me home. When I got it back to the front of my home I tried to start it just for kicks, and what do you know it started!

Fast foward until about a week and a half ago. The XJ had been sitting in my garage and I had not been driving it since this incident while I worked on various other things that needed to be repaired. I never got a check engine code but finally did get a check engine light about a week before I replaced my crank position sensor (with an Advance Automotive replacement) as the code said there was a fualt between the pcm and the crank position sensor. I previously replaced the crank position sensor with an AutoZone sensor about 3 years ago. So much for "built to last"!

So all has been fine for about a week and a half until tonight.

I gave my XJ a few full throttle runs this evening, and about a mile or two later it died again It didn't so much die as it was running really rough, "pinging" if you will, and the RPM's were dancing between 0 rpm and about 500 rpm or so. Regardless I turned it off and restarted, drove about 3 miles further until it died on me again. This time I wasn't able to successfully restart it. Twice or so I was able to restart it but it died again only after running for about a second. It would crank but not fire. So I waited on the side of the road about 15 minutes or so (at this point I was about a half mile from home) and then it finally started. The last few blocks to home it was running rough, pinging again, RPM's dancing. Died in front of my home, and would not restart.

At first I suspected the fuel pump as I couldn't hear it prime. Although it seems to be rather quiet as I found out and the annoying buzzing as well as my electric fan setup seemed to mute the sound of the fuel pump on the side of the road. I switched around my starter, auto-shut down relay, and fuel pump relays to no avail. I noticed that my fuel pump will only prime during the first few off-to-on key cycles. Is this normal?

Anyay I do have plenty of pressurized fuel in my fuel rail, I am guessing the fuel pump is not the problem. I did notice a faint noise coming from the PCM, almost like a buzzing or squealing....while I was parked on the side of the road. Perhaps the PCM is bad? I thought that was fairly unlikely!

In 2007 I replaced my oxygen sensor with a Bosch unit. In 2006 I installed an AutoZone ignition coil (I know, not the best choice!)

Besides that, my throttle position sensor, idle air controller, coolant temp sensor, and intake air temperature sensors were also replaced in 2008. I pulled them out of a 1994 Cherokee with low miles.....not new, that's for sure, but with a heck of a lot of use on them compared to mine! In 2006 I also replace the cam sensor under the distributor cap with a new unit from a small local car parts store.

My plugs are less than 30,000 miles old and my distributor cap and rotor button are the same age. I have AC Delco silicone plug wires which are a few years old as well.

I did not check for spark but obviously that is what I am lacking since I have air and fuel. What else can there be?

About a half hour ago at 2:30 am I went back out to try and see if I could start the XJ. No luck, just crank, when all of a sudden, on my second try, it fired up. But only for a second, then it died again, and would only crank after that. No check engine light either. Still have pressurized fuel in the fuel rail. And the pump is priming, but only on the first few key cycles. Then it will not prime after that.

Any ideas? That would be greatly appreciated!

(1995 Cherokee, 4.0 liter, AW4, OBD1)
 
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Buzzing from the PCM? That doesn't sound good. It does sound like a fuel pump issue with the pinging, but it could be the PCM failing and cutting the injectors. I would recommend getting a noid light and seeing what the injectors are doing when it doesn't start.
 
What you describe is classic for a CPS failure. First clean the connector and reseat. Sometimes it is simply corrosion.
 
I agree with hoppenbrowers to check fuel pressure with an actual fuel pressure gauge. Just because you have a good spray of pressure at the schrader valve on the fuel rail, that doesn't mean that you can't have a fuel delivery problem.

As for the crank sensor, cleaning the connector with electrical contact cleaner is never a bad idea. When it doesn't start, testing it with a meter "may" give you some valuable data. If you have to replace your crank sensor again, I would definitely purchase it directly from Jeep. I have had mixed (poor) luck with aftermarket crank sensors. Quality is questionable with them and although many work out of the box, the longevity just isn't there.
 
I will have to see if I can get a fuel pressure gauge. I'd be pissed if it was the crank sensor since I just replaced it!

I forgot to mention in my original post that I also swapped in a MAP sensor last summer from that low mileage XJ. I grabbed a whole bunch of sensors for it since it had such low mileage!
 
Well I tried to start it today, no luck. Still getting fuel, but no spark. Pulled a plug wire, no spark there. Also pulled the wire off of the distributor cap that leads to the coil, no spark there as well.

I swapped in my auto shut down, starter, and fuel pump relays last night when it died on the side of the road. That didn't help.

I swapped the 3 relays again today, and I tried to crank it, and all of a sudden it started.

Shut it down a few times and it restarted without an issue.

Dunno...

The PCM still emits the very faint noise. I am not sure, it might have always done that. I never put my ear right beside the PCM until last night!
 
Took it on a roughtly 2 and a half mile trip last night to my shop. It made it, no problem, no stalling, ran perfectly the entire way.

My initial no-start problem occured the same day I welded up my exhaust with a 110v flux welder. I was thinking either it was a coincidence (garbage AutoZone crank sensor) or that I possibly fried the crank sensor with the welding. Unless I fried the PCM somehow, who knows, like I said I am going to try and get my hands on another PCM for cheap from the bone yard.

Now that it works I certainly don't know what's wrong. It's both good and bad at the same time - can't trust it for long trips though either way!

Going to weld up my OTK today......finally got 220v installed in the garage last night.
 
You did/are disconnecting the battery when arc welding, right?
 
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