memento

Hey all,

First post here. I've frequented this forum for a long time now and finally I need to make a post looking for some help. For some context, I'm no mechanic by any stretch of the imagination but I've done as much work on my Jeep as I can over the years I've owned it. I'll do my best to explain my experience/issues.

I have a 2000 XJ Limited 4.0 6cyl. In the past I've had issues with the CPS and PCM. I've had the issue of stalling while idle(CPS replacement fixed this). Then it wouldn't start for anything no matter how many times I cranked. Got a new PCM and no more issues. It's been mechanically fine for about 2 yrs now.

Now the issue I'm having is arguably worse, the Jeep will completely shut down while driving. Accessory power/ dash lights etc. stay on but I lose all power to the vehicle and power steering. Got me on I-95 the first time so it was definitely really a scary experience. Takes some cranking to get started again. I haven't counted how many times I turned the key but I would say about 20-30 seconds of trying before it would start up. I've since avoided the highway and am still having it start to happen after about 25 mins of driving driving 40-50mph on smaller roads. I usually take my jeep in to a local shop to get my maintenance done, they couldn't replicate the issue in the shop and were kind of at a loss for diagnosing. No check engine lights come on. The only CEL I've had recently has been from a gas cap I replaced and haven't seen it since.

I've been digging in the forums everywhere and I see there are a few recent posts from users with very similar issues regarding the CPS and PCM, but I've replaced both within the last 2 years (not sure exactly how long but definitely since 2020).

The only other things I can think of would be replacing the ASD relay, I've seen some similar symptoms reported online when that fails. It doesn't buzz like some I've seen so I'm not sure if that would be it. Then the other place I'm thinking would be somewhere in the fuel system? Fuel pump? I don't have a tool to test fuel pressure so I haven't done that yet but I'm out of ideas.

Hopefully I've included enough information for somebody to hopefully give some ideas as this is my work vehicle and really need to get this thing road safe again. Thank you very much in advance for any advice!

exasemech

Unfortunately the fact that the CPS was replaced 2 years ago doesn't mean much if it was an aftermarket part.
But before we go there when it dies what does it take to get it running again??

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memento

Thank you for the reply. It takes a little bit of time to get started back up. I would say about 20-30 secs of intermittent cranking to get it started back up. Doesn't seem to be very consistent however. As an example while driving today it shut down on me going about 50mph. Pulled over, took me about 20 sec to get it to start up. Drove for maybe another 10-15 seconds and shut off again. This time it started up pretty quickly with only one or two key turns. After that I was able to drive for about 5 mins headed home before it did it again, but this time while idling. Started right back up that time and got me home after that which was about 20 mins of driving from that point. Didn't pay attention to actual miles on the trip because I just wanted to get off the road. Hopefully this helps.

memento

Forgot to quote your message in my reply to notify sorry about that still getting used to actually communicating here.

exasemech

I'm trying to avoid the parts cannon here; the only way to do that is by doing some diagnostic thinking.....and some basic maintenance. So thinking out loud........

Things stop running when they lose spark and/or fuel. That can happen because of bad component or funky wiring to component.
we're dealing with a 24 year old vehicle so anythings possible.
,............

It runs okay until it doesn't, and dying happens after it's driven for a while ie warm
Whatever it is isn't setting CEL .so among other things isn't seeing misfire.

So best way to try to narrow down the options is to try to figure out what DOES work.

If your concerned about the relay replace it.

Buy a fuel pressure gauge. Sometime when the thing won't start hook up the gauge . If you have pressure, it isn't fuel, if you don't, then it's either the pump or the pump is losing electrical power. If your going to drive an old vehicle you gotta have tools.

Checking for spark quickly for an intermittent problem with the COIL RAIL ON A 2000 is tough. At least clean with contact cleaner& reseat connectors to coil rail,cps, cam sensor ,tps and pcm

And if your 2 yr old CPS wasn't a Mopar I would wonder about it...

At least that's what I would do to start.

Edit: all the above assumes you have already done the usual stuff:: battery voltage good, battery cables good, grounds good, looked at all the wiring for breaks/bad insulation. We're back to the old vehicle thing.

Jeepwalker

When it does start back up, it sounds like it runs fine, right? And it'll sit and idle fine too, right? And it could idle forever as far as you've known. But on the highway, does it sputter at all before it dies? Or just like the switch was shut off?

The situation where it starts back up, runs a while, then shuts down again tells a little story. Fuel pressure is definitely something to look at. I've had failing fuel pumps where the vehicle would run quite a while when it was cold. Eventually if driven at highway speeds long enough, the fuel pump would heat up enough to lose pressure and vehicle would shut down. After sitting a period (pump cools down), the vehicle would start and idle fine. But after it initially shut down, the time it could be driven until the next shut down was much shorter, like you're describing. But then if the vehicle sat overnight it could be driven quite a while until the fuel pump heated up enough to fail (and the cycle would continue). If there was a way to check fuel pressures when it died, that would be real helpful.

The other thing you could do is to carry a spare spark plug with you. When the vehicle dies, pull off a plug wire right away, and put on the spare (touching bare metal), and see if you have spark. If there's no spark then you learned something important.

jvmarino

One thing you may want to check is ground on engine block. I had an odd engine dying issue that was not consistent, and different from what you are describing, but eventually was solved by cleaning the ground connection. I removed the grounds from the side of the block, cleaned it all up, and then reattached. May not have anything to do with your issue, but is a simple thing to do and costs nothing.