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Matt, Engineer
Category: GMC
Satisfied Customers: 21626
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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GM GMC Savanna 1500: 1999 GMC savanna 5.7LWhile I was

Customer Question

1999 GMC savanna 5.7L
While I was driving the car just died. Will not restart. It does turn over and no problem on gages. Thinking it is a fuel pump problem, I rented a pressure gauge. I checked the pressure and it was between 35 & 40 psi. Now I am beginning to wonder if it is the pressure regulator or the pump. Any suggestions? ??
Submitted: 1 year ago.
Category: GMC
Expert:  Matt replied 1 year ago.
Hello I'd agree that this is very likely to be a fuel pressure issue as these engines need a minimum of 50 psi to start and ideally a healthy fuel pump will push out 56 + psiThe next step is to observe the fuel pressure gauge's needle (after your helper stopped cranking the engine). The needle should descend to about 40 to 45 PSI and stay there for at least 4 to 5 minutes. If the needle DOES NOT stay at this fuel pressure (more specifically: if the needle drops to 0 PSI immediately -by immediately I mean within the first 15 seconds)... you have either a faulty fuel pressure regulator or a fuel injector leaking fuel inside the plastic intake plenum. so based on this it sounds like you may need to replace the pump or possibly the pressure regulatorIf the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Expert:  Matt replied 1 year ago.
Hido you still need help?Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you