Wont start all the time

If the engine cranks but does not start along with the symptoms you describe, it is a classic example of a failing fuel pump. With fuel injection, when you turn the vehicle off the fuel pressure should not drop. This is why you do not have to "pump the pedal" like you had to do with a carberated vehicle to get fuel into the combustion chamber. With the cool temps the pump has more power and can build pressure more readily, the longer it runs the less pressure it can build due to heat from the pump motor operation.

With the vehicle not being driven for a few days the fuel drains back to the tank and the worn fins on the pump are not able to build the needed pressure for the engine to start. The diagnostic test for a failing fuel pump includes key on pressure, running pressure and pressure bleed off. The loss of power while driving indicates the problem is getting worse.

From the information you posted the fuel pump needs replaced.

Hope this helps, let me know.

Dan

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Good luck,

Dan

Was out of town for a couple of days. I am sorry, your symtoms fit the fuel pump perfectly.

The only reason for the fuel pressure to drop that drastically when you turn the enigne off is a fuel leak.
So is either draining back to the tank, a line leaking externally or the fuel leaking into the engine (a leaking injector, fuel pressure requlator, etc.)

How is the pressure on the pump you installed?

The fuel pressure regulator is fairly easy to check, remove the vaccuum line that goes to it and check for raw fuel, if it is present the diapham has a hole in it and the regulator needs replaced.

I did check for Technical Service Bulletins before my first post, but again with your description so closely matching a textbook failing fuel pump; none of them fit as well. There is one (#03-06-04-030F) that deals with drivability concerns and hard starts and lists codes P0171, P0172, P0174, P0300, P01174, & P0175. Is your check engine light on and can you have the PCM codes read? This TSB goes though the GM process for cleaning the injectors that requires special tools and GM top engine cleaner.

I only have TSB"s available to me in a ". Pdf" (adobe reader) format and have never neen able to successfully post those. Send me a private message with your e-mail address and I'll send you all the info I have.

One question; when you replaced your fuel pump did you replace it with a new unit or used? I ask this only for information. I have intsalled used pumps at customers request and have only had about a 50% success rate with them. About two weeks ago I help a friend put a used pump in his mothers 98 S-10 pick up and it took two returns to get a useable pump.

A few more Ideas, send me that message and i'll do my best ro help you out. Thank you once again for your donation, it allows the guys at 2carpros to keep this site up so we can all get on here and share ideas.

Thank you
Dan