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Hi,
I have a 2002 Jeep Grand Cherokee with 4.7L V8. It will not start restart when hot. It has to cool down before it will go again. I have replaced the cam and crank sensors and fuel pump to no avail. The check engine light is not on and there are no trouble codes. When engine is running, it is flawless. It also has 8 new ignition coils and spark plugs. So far, I am a great parts changer!
A Jeep technician said he thinks that it needs the engine wire harness replaced? I am trying to be sure about that before attempting.
I have a multimeter, code reader, and all other mechanical and wiring repair tools. I have repaired many types of automotive electrical issues for many years. This one is making me look bad. Please help.
I left out one other intermittent problem that happens while driving. The voltmeter will suddenly start going down indicating a no-charge condition. This seems to happen at highway speeds. If i slow the vehicle speed to city type driving, the volt meter will come back up and resume charging.
Do you have a scan tool that will display data?
I'm thinking that the coolant temperature sensor could be skewed. After sitting over night the Engine Coolant Temperature should be within a couple degrees of the Intake Air Temperature.
What actually is missing when the engine does not restart after a hot soak?, you got spark, injector pulse, do you see rpm on the scanner? Does it take some time, maybe a minute or so to not restart or does it fail to restart immideately once you shut it off? Vaporlock??
An immobilizer problem would not avoid restarting within the first 5 seconds after shut off, within this timespan the start does not need authorization from the skim.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Have not had a scanner hooked up when it fails to start. Should I do that? What do I need to look at?
When hot, I can shut it off and it will restart immediately once or twice. After that, it will "try" to run, but will not. Sounds like it is trying to run on 1 or 2 cylinders. After waiting approx 1 hour, it will restart and run as if no problem.
I'm thinking of bleeding fuel pressure down at rail and see if that makes a difference.
Just put up the tools. Had to replace starter. It failed from over use with a long period dealing with the hot start issue - 1+ years. I had forgotten to mention that occasionally on initial start up, engine seems to struggle to turn over at first. Then ok afterwards. Reminds me of starting with too much timing advance?
I drove it to get it jot. Then parked it. Turned on and off 3 times and would restart. 4th attempt yielded the all to familiar no start. I immediately went to fuel rail bleed valve and dropped the pressure. It did restart afterwards? So, if this is a potential vapor lock, what needs to be done? Engine is 4.7 V8.
Hi. Vapor lock occurs at low pressure and high temp (i would say extrem temp with high pressure), so i'm afraid i doesn't make sense to me. Anyway i would repeat test.
After starter replaced, I would get a hesitation of the starter to engage. Solenoid clicking. Finally would engage and spin motor. Starter i took off would do same? Thinking poor ground, I improved all battery cable connections. Did not change anything. This is intermittent but does happen quite often.
On the no start that came after the terminal cleaning, I noticed that the tach was not moving. After trying several times, the tach needle moved and it started. The engine check light came on this time. Need to scan the code.
