'96 Chev 1/2 ton 4X (Vortec) won't start after sitting for 8-10 hours

Asked by Feb 28, 2014 at 03:17 PM about the 1996 GMC Sierra 1500

Question type: Maintenance & Repair

My truck starts fine when sitting for up to 8 hours. Longer than that and you're in trouble. It's the weirdest thing how it starts just fine anytime after it initially runs, but if you leave it overnight you're back to the "not enough fuel" problem.I poured fuel down the throttle box and that did the trick. I've replace the plugs and wires and had a tune-up done. One thing I have noticed is an absence of the high pitched whine when you turn the key ... I always thought that was the fuel pump engaging, but if the fuel pump wasn't working it shouldn't start or run anytime.
What's the answer to this riddle?
Sign me - Perplexed !!

2 Answers

104,465

First off I don't advise putting gas or any other type of starter fluid down the throttle body of a vortec engine. The intake is plastic and if it backfires thru the intake you could blow it to pieces. I am still finding parts of my intake in my back yard. I learned that lesson the hard way. Sounds to me like your fuel pressure regulator is possible going bad or your spider injectors are leaking the fuel pressure down over night.

400

Put a fuel pressure gauge on the rail and make sure its sealed tight (no leaks) Run the engine to confirm the 50-60 psi. Leave the gauge there over night and see if it leaks down. If it does, you either have a bad injector (spider) or the fuel pump check ball is leaking. Cranking it should produce the required 50-60 psi needed to start. You mention nothing about running rich but that is also an indicatior of a leaky spider.

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