Jeep won't start once it's up to running temperature

57hemi

57hemi

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Joined
Mar 17, 2019
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Pa
Hi guys, new to the forum and hoping someone can help me out! I have an 03 TJ with the 4.0 and Manuel 5 with 100,000 miles. I just purchased the Jeep and knew of the issue when I purchased it. The Jeep starts every time when cold, but once up to temp it will just crank. After about 15min the Jeep will fire up and run just fine. The guy showed me receipts for new crank sensors, and plugs done at inspection (6 months ago). Jeep has no codes being thrown. Any help would be great! Thanks.
 
Not throwing any codes, and I haven’t checked for spark once warm. I no for sure it’s getting fuel bc I can smell it, and have fuel pressure in the rail.
 
After you start it cold, doesn't run normally and fine until you shut it down and try to re-start it?
 
When it won't start, when turning the key from the off to the run position, can you hear the fuel pump run briefly? Maybe the fuel pump is loosing prime. Next time it won't start turn the key from off to run several times and then try starting again. Mine did this a couple of years ago. Ended up that the fuel pump was loosing prime.
 
dbbd1 said:
After you start it cold, doesn't run normally and fine until you shut it down and try to re-start it?
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Jeep fires right up when cold and runs fine. Shut it off once it reaches temp and won’t re-start till it’s cold.
 
I’ll listen for the fuel pump when I work on it next. Jeep only has about 1/4 tank. Could this affect priming?
 
So, if It starts, I have fuel pressure in the rail then I don’t think it’s a priming issue. I think it’s a spark issue. But not sure.
 
I would move on to replacing the crank sensor.
Hopefully, it's not a PCM issue.
 
57hemi said:
Crank sensor was already replaced
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Wiring harness going to crankshaft positioning sensor could have faulty wires perhaps? It’s above transmission bell housing and is prone to heat. This was my problem six months ago. I had the wires fixed and it’s been fine ever since. The only thing that stomps me is that yours is doing it only after it gets warm. It might be worth it for you to do a good visual inspection of those wires and all alike. Hopefully this helps bud.
 
I think I am having an issue with the wires that are running to the computer on the fire wall. Fired it up, ran it for 20min to get to temp and it wouldn’t start, wiggled the wires going into the pcm and it fired up. I noticed someone had been into the wires and re-electrical taped it. That’s where I am going to start next. Take the tape off and inspect wires and insulation surrounding it.
 
57hemi said:
I think I am having an issue with the wires that are running to the computer on the fire wall. Fired it up, ran it for 20min to get to temp and it wouldn’t start, wiggled the wires going into the pcm and it fired up. I noticed someone had been into the wires and re-electrical taped it. That’s where I am going to start next. Take the tape off and inspect wires and insulation surrounding it.
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That would be a good idea. Mine would cut off at random times. I got underneath it and wiggled wires going to cps and it fires back up. So maybe your issue is the just in a different spot. Maybe just take your time and be thorough looking for any and all problems.
 
New up date, now the Jeep has trouble starting all the time and is throwing an O2 sensor heating code bank 1, and a pending code that is for engine coolent sensor......
 
I think I got to the bottom of the issue, the Jeep finally gave me a code. P0118 (coolant sensor.) Installed new sensor and Jeep fires, runs, and will re-fire when hot. $20 fix and a lot of head aches later. Gauge in the Jeep actually seems like it’s functioning better as well.
 
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