Chasing the root cause of heat soak (2001 XJ)

[JonnyCat63]

Originally Posted by DPG

Resurrecting this one. Hoping for some more insight.

My "00 XJ is having issues. Usually after driving at higher speeds and then slowing down or stopping, it will die. Once that happens, it will not start for at least 15-20 minutes. This has progressively gotten worse over time.

It used to restart quicker and only happen on hot days. Last night it died (around 65 degrees outside) and after 20-25 minutes, I gave up and called a tow truck. Once I got it to it's destination (About 30 minutes later) it fired right up again.

I had just installed the DEI insulation goodies on the fuel rail and injectors, along with the newer 4 hole injectors and O-rings. Same issue. One of my guys thinks it's not the fuel pump, but it sure seems like a good idea to replace it, as it's 18 years old now anyway.

My '00 4.0 liter suffered the cracked head syndrome, so this motor is out of a '99TJ. IIRC, we stayed with the '99 TJ exhaust manifold, but had to do some custom work to mate that to the XJ exhaust. I'll have to look and see if the pre-cat is in there or not. It's not here right now to look at.

Sure sounds to me like I should replace the fuel pump first and possibly remove the pre-cat after that. I don't recall- are there any sensors in the pre-cats? Don't know if I'll have any issues with codes...?

Any updates or insight is appreciated.

Thanks!
Dirk

I'd look at the CPS, too. My 97 had almost the exact same symptoms. Would not start back up after a long hill climb, or at the end of a long day wheeling. At first the problem was once in a while, but then happened with increased frequency. Always started after sitting a while. Finally changed the CPS and all is good. Faulty CPS seems to be a common problem on the XJ's. Hope that helps.

[DPG]

Originally Posted by Talyn

Have you replaced the CPS and/or checked for spark when it dies?

I haven't checked the CPS. Is it common for that to only act up after everything gets hot and then work fine again when everything cools off? Seems like the only time a CPS went bad on me, it just went and that was it.
How would I check that- especially when it's running fine?

I also haven't checked spark, but I can't imagine that would come and go with heat? Once it cools down, it fires right up.

Whatever it is, it has definitely gotten worse over time. Something is degrading or weakening. That's what made me think more along the lines of fuel pump.
I dunno. My specialty is in suspension set up and trouble shooting. Electrical and engine issues have never been my strong point.

Thanks!
Dirk

[DPG]

Also, I've heard people say that their jeep would not start after they shut it off.

Mine has never had an issue with that. It always dies first- usually right after some higher speed driving. Then, It won't start until it cools off, at which point it seems to run just fine again...

I may just have to start throwing some parts at it and see what happens...

[DPG]

Originally Posted by JonnyCat63

I'd look at the CPS, too. My 97 had almost the exact same symptoms. Would not start back up after a long hill climb, or at the end of a long day wheeling. At first the problem was once in a while, but then happened with increased frequency. Always started after sitting a while. Finally changed the CPS and all is good. Faulty CPS seems to be a common problem on the XJ's. Hope that helps.

Thanks!

I had a CPS go out once and it hardly ran at all. No come and go.
I'm gonna try this first, as it's cheaper and easier than the fuel pump...

[XJweasel]

Another PO303 resurrected

I took my 01' to a mechanic to fix a Heat Soak issue. They installed the 2 parts I gave them 56028371AA & CBXCB060. Shield and Insulator

They also changed the plugs and the 3rd fuel injector.

It's now running worse than when I dropped it off. :/

[DPG]

My issue did actually turn out to be the CPS in this case...

[XJweasel]

Thanks

[DPG]

Originally Posted by XJweasel

Thanks

If new plugs and an injector made it run worse before it gets hot, I can't help but wonder if they did something wrong there...

[XJweasel]

Originally Posted by DPG

If new plugs and an injector made it run worse before it gets hot, I can't help but wonder if they did something wrong there...

Yeah, now they're trying to fix what they broke.

It's not throwing any codes so they can't figure it out.

Yes, I went to the wrong mechanic.

[XJweasel]

Ug, now they want $500 for an oil pump. I think I'll DIY that one

[XJweasel]

Okay, took it to an actual Jeep Mechanic and it turns out my fuel pump was bad. :rolleyes