94' Yukon wont start when hot

[list249]

Hello everyone, I have had a low voltage reading for awhile now(4000+ miles), but today My truck would not start. I tried a jumpstart, which brought the voltage up to 14v from 12v, but still nothing, no solenoid click at all. When i left work, it started fine. I made a couple of stops on the way home, at the first i noticed the starter running slower than normal. At the second stop, is where it died. I towed it home, and of course once home, it started right up. I Managed to recreate this problem. I did some light offroading to get the motor really hot and noticed that while cold, i have a solid 14v, but that gradually drops as the the truck warms up to slightly under 12v. The alternator and battery have been recently tested and passed, the battery is new. Also, it is very hot here in Tucson (110 degrees today). I have two other posts on here about my alternator and a vapor lock issue, dont know if they are also related to this problem. Thank you.

 

http://www.gm-trucks.com/forums/topic/201919-bad-alternator-94-yukon/

http://www.gm-trucks.com/forums/topic/202082-can-a-tbi-vapor-lock/

[list249]

I just double checked, it starts cold but as soon as it up to operating temp, it wont. I tried starting it halfway to operating temp and it did. Starter sounds weak.

[Dnt]

Not real clear on your symptoms. Are you saying that the engine will not turn over after it gets warm? or that it tuns over but does not start?

If it is not turning over after getting warmed up then try this easy little test first. Pull the electrical connection off on the AC compressor clutch and try the starter.

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[list249]

it does not turn at all, no solenoid click, not a sound at all. Will try the A/C compressor now.

[list249]

I had a little time today so i stuck a voltmeter on my battery with the ignition on, it reads the same as my dash gauge, 12v. So my battery is bad, or not charging. Its been reading low voltage since i bought it, and he told me it had a bad battery at the time. I'm thinking the guy put an autozone special alternator on it before he sold it, it looks pretty new. Perhaps its been slowly going bad, and now the heat finally did it in.

[list249]

It was a bad starter, tested good the first time. He ran it a second time and it popped the breaker on the testing machine. It had a short in the starter, it was causing my low voltage. With the new starter in, voltage stays above 13v.