Question about 1999 GMC Yukon Denali

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99 Yukon 5.7 won't start, ONLY when it rains

Problem for several years, multiple dealers, still no luck.
We thought we had it when we replaced the MAP sensor in Jan 08, but doing it again. I still think it has something to do with the lower air pressure when it rains. The problem has NEVER occured by washing the truck, and one shop dowsed it in water repeatedly to try to get it to induce problem. It only does this when it rains. No code is ever indicated during or after the problem.
Vehicle will turn over a couple revs when key is reset (and fuel pump recycles). It turns over a few revs then quits. If you do not reset the key, and try to push the key to start from the ON position, it does not catch any revs (no fuel, because no reset) thereafter.
Crank sensor, dist have also been replaced with various tries by dealers, they did nothing, no difference. MAP sensor replace seemed to solve the problem for a couple rains, until now (Live in AZ.)

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  • jc_nshmba Dec 02, 2008

    The problem has gone on a coupole years and most all of those have been replaced. My mechanic just determined that it is either the BCM/VCM or anti-theft module that gets crossed with the humidity or rain, and as a result shuts off the fuel. Apparently also could be a simple fray anywhere in the wires to and from those modules. So, wwe think we know what it is, but no exactly.

  • Anonymous Mar 08, 2009

    Same exact problem for my 99 Yukon, only when it rains.

  • Anonymous Mar 31, 2014

    I have replaced coil pack & wires distributer,plugs and wires, roter button, I tried covering motor when I knew it was going to rain, cked fuel pressure,it gets fire, air not sure.... and still when I go to start it after a rain it wont start until whatever it is dries out. sometimes a day sometimes two! what can this be? PLEASE!



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One of my problems was with a 99 Yukon SLE and it wouldn't start when the air temp was below freezing. It would crank, but for whatever reason the fuel pump would disengage, I used to have to prime the throttle body with gas to keep it running and as soon as the engine got warm, voila! I know it doesn't sound like the same issue, but hear me out. I bought the SUV secondhand. It had an aftermarket security system installed, and according to the dealer who fixed the problem, the original installer tapped into the main wiring harness and made a mess. After replacing the wiring harness, this and a other problems miraculously disappeared. If you have anything tapping into your main wiring harness you may be getting moistur and causing a short. Hope this helps, and if not ... sorry for wasting your time.


Posted on Apr 20, 2009

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When the dist. was replaced, did that include the cap, rotor and ignition module? what about fuel filter? coil?

Posted on Nov 28, 2008


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