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Unread 09-06-2012, 06:12 PM   #1
87manche17
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1987 MJ Comanche 
 
Join Date: Jul 2012
Location: Harlan, Kentucky
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Will not start when warm

I went to the grocery store today in my 87 MJ, and when I started it while it was cold it started and ran fine. When I turned the truck off to go in the store I came back out and it wouldn't start. I got a ride home and let it sit in the parking lot for about an hour. I came back and it fired right back up. My conclusion is it will not start when warm, Ive already changed my CPS on the bell housing still no change. It has a new coil and control module so it cant be that. I'm thinking its the stator in the distributor, could that be it or something I haven't though of?

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Unread 09-06-2012, 06:15 PM   #2
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by 87manche17 View Post
I went to the grocery store today in my 87 MJ, and when I started it while it was cold it started and ran fine. When I turned the truck off to go in the store I came back out and it wouldn't start. I got a ride home and let it sit in the parking lot for about an hour. I came back and it fired right back up. My conclusion is it will not start when warm, Ive already changed my CPS on the bell housing still no change. It has a new coil and control module so it cant be that. I'm thinking its the stator in the distributor, could that be it or something I haven't though of?
The stator in the distributor is certainly a primary suspect.

When they fail thermally (heat related), the 4.0 engine will continue to run on the latest signal from the stator, but when the engine is turned off, it won't start unless that component is giving valid input data to the computer.

I'd recommend you replace that component. Not particularly expensive and shouldn't be too bad to replace. Refer to a maintenance manual if you have one.

Good luck and keep us updated!
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Unread 09-07-2012, 10:47 AM   #3
87manche17
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ok thanks
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Unread 09-07-2012, 12:00 PM   #4
Cosmo13
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I have an 89 xj and I had the same problem it ended up being my fuel pressure regulator. First start of the day it would start no problem but if I went anywhere and it only sat for a little bit I would have a hell of a time starting it. If it sat for a few hours it would start up no problem.
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Unread 09-07-2012, 12:13 PM   #5
ltrail
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Try giving it half throttle and then cranking. Had a similar issues which was a Cts. Cts was bad and computer seemed to think the engine was cold thus dumping ton of fuel for cold starting. With pedal half way down it fires right up.
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Unread 09-08-2012, 11:56 AM   #6
87manche17
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My CTS is brand new so it cant be that. But im going to try the stator first and see what happens.
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Unread 09-08-2012, 04:46 PM   #7
87manche17
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I installed a new stator and it did not help. Its still flooding itself out trying to start. I think I need to replace my MAP sensor but Im not sure.
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Unread 09-08-2012, 04:56 PM   #8
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by 87manche17 View Post
I installed a new stator and it did not help. Its still flooding itself out trying to start. I think I need to replace my MAP sensor but Im not sure.
Map sensor can be tested with a meter and a manual (or procedure) And be sure that the vacuum line leading to the map sensor is pulling good vacuum.

Here is a link to an article that can be helpful in testing RENIX sensors.

http://www.lunghd.com/Tech_Articles/...iagnostics.htm
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Unread 09-08-2012, 07:27 PM   #9
87manche17
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Ok my CTS is not even hooked into the block itself. I thought the one on the back of the head was a "actual" sensor, so I didn't hook it up when i changed motors. Ill hook it up tomorrow and go from there.
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