1999 5.7l 1500 4x4 The truck will only start if I put fuel in the throttle body and will stay running with no issues. I can shut it down and start it again when its warmed up. I replaced the fuel pump 2 years ago and it has good pressure, I also just replaced the fuel filter. I am at a loss here I picked up a fuel pressure regulator but I am reluctant to take off the upper intake if I am not sure that will solve the problem. There has been no check engine light and motor cranks strong with good spark.

That sounds like the fuel pump is going out and check fuel pressure,specs are 60 to 66 psi.General rule with GMs,will not run under the lowest fuel pressure.Was the fuel pump an aftermarket pump?Most aftermarket pumps are junk.Only two places to get the fuel pump are the dealer or your nearest Carquest parts store.Carquest's fuel pumps are now made by Delphi,made the switch to Delphi ditching Airtex for their fuel pump supplier and now last longer.

I am getting 62 psi on the fuel pump from NAPA. Do you think it could be the pressure regulator? I have been also been thinking maybe it has something to do with the aftermarket remote start I put in 3 years ago. But that really makes no sense because it stays running and drives after I put fuel in the throttle body.

How fast does the pressure drop off and to what psi, , when the key is turned off? Assuming an accurate gage, 62 should start the engine, if the regulator or injector lines are leaking then no, but you would smell some raw fuel.