I've been lurking for quite a while since I bought my jeep a few years ago. I've always been able to diagnose any issues I've come across by searching and reading posts and tech write-ups until now. I have a 2000 4.0 AW4 4x4 and I've been chasing an intermittent no start issue for a few months.
The issue only arises typically after short drives around town. Drive to the store, come back out a while later and no start. I say its short term because eventually it will fire up again. Some times its just a few minutes, sometimes its 15. Once it starts it runs perfectly fine. No misses or hesitations of any kind. I'm led to believe it's a thermal failure of some kind but cant figure it out.
Several parts have been replaced over the last 6 months; however, most were replaced due to unrelated issues. The CPS (Mopar), TPS (Napa), and fuel pump relay have been replaced. The injectors were swapped for 784's when had one fail a few weeks back, but the no start was preexisting. I'm not sure where to go from here. There's no CEL or DTC's. Any suggestions will be greatly appreciated. Thanks!

 

When it fails to start what's missing fuel or spark?

 

What condition is the heat shield blanket under the injectors like?

 

Spark I assume as there is pressure at the rail. I haven't put a guage on it yet, but will next time it happens. It never seems to do it when I'm trying to troubleshoot it.


Heat shield blanket has seen its better days, but this seems different than the typical injector heat soak issue.

 

Most times it wil fire for a second then die. If I continue to turn it over after it dies it doesnt even try to fire again until I cycle the key. Of course as with everything there has been a few times when it won't do the fire and die, just no fire. In both cases I can hear the fuel pump prime

 

Just for s&g did you check the spark plugs and see if they are gapped right or wet when it happens or when it just does a no start do you mean that it doesn't even try to tern over and just does nothing

 

Heat soak symptoms are when the hot engine starts it sounds like it's running on 3 cylinders for about a minute, then clears itself.

 

Maybe it's your Camshaft Position Sensor.

Generally if he CPS is screwed up it will trigger a DTC/CEL. But.....

 

No I haven't pulled a plug to check. It always happens at an inopportune time when I'm not prepared to tear it apart. I just wait a little and it eventually starts then runs perfectly fine on the way home.

There's times I can drive it for days without it ever happening

 

I would think that if it was the cam position sensor there would be other symptoms, because aside from the times it doesn't start the dang thing runs awesome

 

He guys just wanted to update this thread in hopes of finding some kind of answer for this damn thing.

I am still having the same problem with an Intermittent no start. Long story short the TPS, MAP sensor, coil pack, fuel pump, have all been replaced with several hundred miles on them. The CPS was replaced about 18 months ago as well.

I thought i had it narrowed down to a problem with the MAP circuit seeing as when it doesn't start (cranks but no start) if I unplugged the MAP sensor the engine would fire and run for a few seconds then die. Once that happens I can plug the sensor back in then it would fire and run fine. Replacing the MAP sensor did not fix it.
That led me to believe it was the ECM. Swapped that for another and still no change. Occasional no start. I'm at my whits end with this thing. I've never had an issue persist for this long and not been able to diagnose the problem, and never before have i turned to throwing parts at something like I've had to do with this thing.

Please help with any suggestions. Thanks

 

Sounds the the issue is with the connector/circuit to the MAP.