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Ivan, ASE Certified Master Technician
Category: Chevy
Satisfied Customers: 4871
Experience:  ASE Master Tech. 20+ years experience. 9 years self employed. Expert on AUTOLAB Radio Show
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2000 GMC Sierra 1500: wont start..sitting overnight..Fuel pump..relay

Resolved Question:

2000 GMC Sierra 1500 4x4 (5.3 engine) won't start after sitting overnight. Fuel pump is new, relay is new. after cycling key several times, it usually will start. When it does start, it is not loaded up and runs fine and starts over and over if not sitting for more than several hours. Starting to think it may be the cam sensor or connector but I don't want to keep chasing fantoms. What do you think and what does a dealer charge for your recomended repairs.
Submitted: 8 years ago.
Category: Chevy
Expert:  Ivan replied 8 years ago.

HelloCustomer the first thing you need to concentrate on, is fuel pressure. You need to check for two things, that pressure is within spec and that pressure holds and does not drift down after you shut the truck off. It is natural for pressure to slowly drift down over a 30 minute period, but not to 0. If it drops quickly it would indicate either a fuel pump or a fuel pressure regulator. This is where you need to start. Fuel pressure has to be 55-62 psi with the engine off and the key on.and should be there immediately when cranking the truck. Immediately after shutting off the truck, it should hold rock solid.


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Customer: replied 8 years ago.



Just one follow up question before I check fuel pressure. Does a low fuel pressure condition also cause the spark plugs not to fire? I may have forgot to include this in my original question but I am getting no spark.

Expert:  Ivan replied 8 years ago.

No if you have no spark, you may have a crank sensor related issue. The fuel pump would have no affect on spark, but a faulty crank sensor would cause the injectors not to fire as well. This is where a scan tool becomes a major part of the diagnosis. I am going to send you the complete procedure, schematic and descriptions. Take this info, review it, a fuel pressure test would be good, but I think you are going in a different direction. Review this info, see how comfortable you are pursuing this on your own. Let me know. This is where voltmeters and scopes come in handy for getting info.



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