Jeep Won't Start When Hot
07-03-2012, 08:17 AM
#1
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Year: 1988
Model: Comanche
Engine: 4.0
Jeep Won't Start When Hot
91 XJ, 4.0 has been in the garage for a few months while I put a lift and some other stuff on it. Only thing I changed on the engine was aftermarket header, 99+ intake manifold, and 703 injectors. Exhaust only has header and downpipe, no muffler. I have to drive it to the exhaust shop to get exhaust welded up. Last night, I finally got everything back together and it cranked right up. I drove it 3/4 of the way around the block and it died. I thought it was out of gas, if not, it was super low. I went and got gas, came back, cranked for a minute and with pumping the gas it started. I then pulled it back in my driveway, closed up the house and was going to go for a test drive. I crank and it won't start. It was late, so I said fu*k it, and I went to bed. This morning I go out, and it starts in the first two seconds of cranking. Did I forget to hook something up? I don't see anything I missed. Open to suggestions. Thanks in advance!
07-03-2012, 10:15 AM
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Year: 2000
Model: Cherokee
Engine: 4.0
How did it behave when it died? Did it sputter or anything, or just cut out completely as if you turned the key off?
Could be electrical. Could be related to the fuel pump. Oxygen sensors hooked up? There's a lot of reasons this could happen, so you need to carefully examine the symptoms.
Could be electrical. Could be related to the fuel pump. Oxygen sensors hooked up? There's a lot of reasons this could happen, so you need to carefully examine the symptoms.
07-03-2012, 01:04 PM
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Year: 1988
Model: Comanche
Engine: 4.0
sputtered. like out of gas. all sensors are hooked up. all vacuum lines are hooked up. just got off work, so i'm gonna go mess with it now. anyone else have any input?
07-03-2012, 01:08 PM
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Year: 1999
Model: Cherokee
Engine: 4.0
I had a Civic that would do this when it got really hot and I would stop to get some gas or something.
I never resolved the problem before I sold it but I know my fuel pump was going out.
In your case it might be a fuel pump relay or something electrical in the pump that doesn't like when its hot out. I would start by checking/replacing your fuel pump relays.
I never resolved the problem before I sold it but I know my fuel pump was going out.
In your case it might be a fuel pump relay or something electrical in the pump that doesn't like when its hot out. I would start by checking/replacing your fuel pump relays.
07-03-2012, 03:29 PM
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Year: 1988
Model: Comanche
Engine: 4.0
couple things i just noticed. temp gauge doesn't seem to be working, and I know it did before. also, if i rev it up, or give it gas and hold it, it doesn't smoke, but when I let off the gas, I get white smoke.
07-03-2012, 03:33 PM
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Year: 96
Model: Cherokee
Engine: 4.0
white smoke is a product of running rich, its the blue smoke thats really bad.
Ive had the same kind of issue when out on the trails, I think I may be vapor locking (yes I know, its EFI) but I guess the fuel rail could be getting hot enough.
Ive had the same kind of issue when out on the trails, I think I may be vapor locking (yes I know, its EFI) but I guess the fuel rail could be getting hot enough.
07-03-2012, 03:51 PM
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Year: 1988
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small wire towards back of engine on drivers side was disconnected. I think it is the temp sensor for the gauge. I hooked it up, and it seems to be starting fine. picture of said wire in a minute.
Last edited by harleys; 07-03-2012 at 04:01 PM.
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07-03-2012, 04:17 PM
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Year: 1988
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just drove it around the block, seems like that fixed it! must do something besides just the gauge, right? why would that make it not run? if you look at the pic, there is a small hole in the vacuum line for the map sensor as well. i replaced that vacuum line.
07-03-2012, 04:23 PM
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Year: 90,84
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Engine: 4.0,2.5
BINGO! Floating around here and there are posts......Now humor me...get it warmed up enough the gauge should be reading, then unplug your CPS and check the gauge again.
Besides the gauge "lore", a CPS might fail hot as well...
Whoops Again....I never won a typing contest!
Besides the gauge "lore", a CPS might fail hot as well...
Whoops Again....I never won a typing contest!
Last edited by DFlintstone; 07-03-2012 at 04:27 PM.
07-03-2012, 04:36 PM
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Year: 90,84
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Cory, white smoke might be trans fluid from a chevy with a vac diaphragm on the tranny, blue(ish) smoke is oil, and rich is BLACK!
Harleys, just for fun, did you know yours should do this? (codes are listed in (info threads)
The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!
Harleys, just for fun, did you know yours should do this? (codes are listed in (info threads)
The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!
07-03-2012, 06:43 PM
#14
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Year: 1988
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well, i just drove it around town. stopped and ate, went to a couple stores to take the wifey shopping, and it started fine every time. hopefully it's fixed.
Last edited by harleys; 07-03-2012 at 09:12 PM.
07-03-2012, 09:35 PM
#15
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My guess is bad grounds. My '87 would start fine then after warmed up, wouldn't start. Then it would etc. When it was running, I moved wires around on the right side of enginer. Suddenly, it died. Dipstick grounds were really bad. Cleaned them up and all good now. Not sure if your grounds are the same.