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Old 01-26-2014, 08:51 PM   #1
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jeep won't start after it is warm

the last few days i have had problems with starting my jeep once it gets warmed up. the temp gauge usually sits right at 210 but I've read before how inaccurate the yj gauges can be. if i warm it up in the morning and let it heat up i can shut it off and start it up as many times as i want, but if i drive it 10-15 minutes and shut it off then it won't start up. the first time it happened i thought i had a bad terminal connection so i took them apart and cleaned them and it started right back up, but after a few days of this i have realized that it just has to cool down before it will start again. any ideas on what might cause this?

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Old 01-27-2014, 07:12 AM   #2
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Sounds like you could be getting a bad coil. It works fine until it warms up.

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Old 01-27-2014, 07:37 AM   #3
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the last few days i have had problems with starting my jeep once it gets warmed up. the temp gauge usually sits right at 210 but I've read before how inaccurate the yj gauges can be. if i warm it up in the morning and let it heat up i can shut it off and start it up as many times as i want, but if i drive it 10-15 minutes and shut it off then it won't start up. the first time it happened i thought i had a bad terminal connection so i took them apart and cleaned them and it started right back up, but after a few days of this i have realized that it just has to cool down before it will start again. any ideas on what might cause this?
And by not starting I mean that the starter doesn't engage when it gets hot. So I'm leaning towrads just replacing the starter but I want some other opinions before I do that
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Old 01-27-2014, 11:09 AM   #4
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Take it and have it bench checked
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Old 01-27-2014, 12:43 PM   #5
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Take it and have it bench checked
Will they be able to read anything if the problem only happens when it is hot and it won't be hot when I take it to them?
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Old 01-27-2014, 01:19 PM   #6
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Well, since the starter is only used when you start it, I'm not sure how heat could be the problem unless the heat from the engine (and other odd factors such as thermal expansion of dissimilar metals) is affecting it. You could have it tested but I'd be leaning toward something else causing it.
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Old 01-27-2014, 02:57 PM   #7
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Well, since the starter is only used when you start it, I'm not sure how heat could be the problem unless the heat from the engine (and other odd factors such as thermal expansion of dissimilar metals) is affecting it. You could have it tested but I'd be leaning toward something else causing it.
At first I didn't think heat could be an issue with a starter either which is why I thought it was a battery connection issue at first. But then I realized that it was the time it took for me to disconnect and reconnect the battery that had an effect rather than what I was actually doing. According to my mechanic the heat would cause the connections in the starter to separate so that it wouldn't start and then reconnect as it cooled off. Sounds logical to me but I just wanted some other opinions
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Old 01-27-2014, 03:36 PM   #8
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According to my mechanic the heat would cause the connections in the starter to separate so that it wouldn't start and then reconnect as it cooled off. Sounds logical to me but I just wanted some other opinions
Yup. That's the thermal coefficients of dissimilar metals I mentioned. It's very possible and has surely been the cause of many a Jeeper's follicular losses.
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Old 02-15-2014, 06:20 PM   #9
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Well I finally got around to chasing this issue after getting tired of sitting atnthe gas station for 20 minutes the other day waiting for it to cool off. I've ruled out issues with the starter and electrical issues between the ignition and the starter. Once it warms up and won't start I have power at the starter and can start the jeep by shorting out the posts. Pulled the starter and had it bench tested and it checked out fine. Replaced it just in case and still had issues. So I returned it and put the original back on. So now I'm back to square one. What issues would cause me to have power at the starter, but it not engage once it reaches running temperature?
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Old 02-15-2014, 06:59 PM   #10
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Don't wanna sound like an ass, but have you checked / replaced the relay? I had a similar issue with mine, but it was more sporadic than what you describe your issue to be. An ignition "guru" at my local Napa suggested I remove the relay when it didn't want to start, and jump pin 87 to pin 30 with a small piece of wire. By God, it worked, the starter took off spinning, and since I had the key on and gear shift in neutral, it fired right up. $16 at Napa for a new relay, and my starting problems disappeared. I don't suggest you jump those exact pins on your starter relay, but I would consult a Napa sales rep. My guy looked it up on his computer to find the exact pins to jump. Good luck!
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Old 02-15-2014, 07:01 PM   #11
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Don't wanna sound like an ass, but have you checked / replaced the relay? I had a similar issue with mine, but it was more sporadic than what you describe your issue to be. An ignition "guru" at my local Napa suggested I remove the relay when it didn't want to start, and jump pin 87 to pin 30 with a small piece of wire. By God, it worked, the starter took off spinning, and since I had the key on and gear shift in neutral, it fired right up. $16 at Napa for a new relay, and my starting problems disappeared. I don't suggest you jump those exact pins on your starter relay, but I would consult a Napa sales rep. My guy looked it up on his computer to find the exact pins to jump. Good luck!
It was my understanding that if it was something was wrong in the relay then I wouldn't have power at the starter when I turn the key. Am I wrong in thinking that?
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Old 02-15-2014, 07:19 PM   #12
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I'm not an ignition expert, but there is constant power to the starter from the hot wire off the battery. On my '93 4.0, there are only two wires going to the starter. One from the battery, and the other from the relay. Honestly, I never checked for voltage at the terminals while attempting to start. If you have power at the solenoid from the relay while turning the key and it still won't start, I would replace the starter. But I read that you tried that already. I know that some Jeeps have another solenoid on the firewall, not sure if yours does or not, but that would probably be worth looking in to. Mine does not. I hate shotgunning parts, I always try to start at one end of an electrical problem and go towards the other. I wouldn't know how, but perhaps there may be an issue with the ignition switch itself? I only suggested the relay because my issue was similar to yours and it's a cheap and easy part to replace. Regarding my last post, jumping the two correct relay pins is nice, because it takes any potential issue with the relay out of the equation and sends the juice directly from the ignition switch to the starter.
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Old 02-15-2014, 07:25 PM   #13
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Awesome. Thanks for the info. I'm very limited in my electrical knowledge so any info I can get helps. Sounds like that is my next step
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Old 02-16-2014, 04:49 PM   #14
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Check your ground cables and straps. They will go from battery to frame and body and from engine to body and frame. There is so much electronic stuff on these Jeeps that there are several separate grounds. If rust or corrosion gets between the connection and the ground it can not let the circuit complete. Just make sure they are clean and tight.
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Old 02-18-2014, 01:04 PM   #15
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alright so i replaced the starter relay today and still won't start when its warm. i finally got my hands on a schematic and the only two parts left in the ignition system are the the ignition switch and the pcm. i highly doubt the switch would be affected by heat but a new pcm is 300 bucks. anybody have any experience with pcm issues before i try to replace it?
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Old 02-18-2014, 01:05 PM   #16
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or does anyone know any reasons why it would not be the pcm?
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Old 03-24-2014, 11:31 AM   #17
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I have the exxxxxaaact same problem u have man.... I replaced my pcm about two months ago... It did nothing. I may try to replace my thermostat just to see. Its a cheapish part
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Old 03-24-2014, 12:09 PM   #18
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Right now I just have my starter hot wired through a push button. I've narrowed it down to either the PCM or the ignition switch but I just haven't had time to work on it. The switch isnt easy to get to but its way cheaper so hopefully if I have time I will be doing that this week

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