98 silverado 5.7L. Symptom is a long crank (3-5 seconds ) only when engine is warm and has been shut off for 1-4 hours or so. if I turn it off and restart within 30 minutes or so, it starts right up ..Fuel pressure slowly bleeds off. pressure when running is great, drives great. Fuel pump was replaced 5 years and maybe 15k miles ago with delphi unit, Just replaced the stock injectors with a Standard Motor Products MPFI- , twice. No change. I Visually inspected the fuel lines and cant see a leak anywhere, couldn't really see top of tank though ...like I said, Fuel pressure is great when running 56-57, jumps to 61 when I goose the throttle, drives great under load. I have heard that there may be a one way valve somewhere. Thats the only other thing I guess it could be. Is it part of the pump and whole unit needs to be replaced? Thoughts? Thanks.

 

There4 is a check valve built into the fuel pump assembly. You can either replace the fuel pump assembly or add a check valve into the fuel line near the gas tank.

 

If it's not happening in the AM cold start after sitting overnight, makes me think you have something else going on. Have you tried turning key off & on several times to get pump to prime the lines before starting?

 

so, after a about an 1.5 hrs of sitting , I cycled the key 5 times, did not have my gauge hooked up, but started it . It had the same long crank... I would have thought the pressure would have been built up and started normally. going to try it again with the fuel press gauge to confirm pressure is up. I replaced the crank sensor, because I heard those can act up after a hot soak, no change.

 

I did a hot soak start after 4 hours of being off, pressure was down to 10 psi, turned key to ON and pressure jumped up to 55 immediately, then cranked it and it took about 3 seconds to start. Ran it for about 10 seconds then shut it off and, restarted and it fired right up. Also tried cycling the key ON several times and no change. So, it usually starts right up when cold and also when quickly restarted, but has a long crank after sitting for 1-4 hours or so. I know the pressure shouldn't be dropping, but It doesn't appear to be fuel pressure related. It wouldn't be the first time Ivel dealt with two problems that were not related.. I'm at a loss...

 

Ok , so after speaking with the shop that did the initial diagnosis, they brought up the point that in a hot soak condition, the fuel in the intake area where the engine is HOT, is probably vaporizing as the pressure drops and even though the pressure rebuilds quickly, it has to push the vaporized fuel out before it'll start, thus the long crank only after hot soak.. --Recommendation= New fuel pump. Just ordered a GM pump. Will return and report...

 

Well..., new pump made no difference....I plugged the supply line where it connects to the intake and then pressurized with the pump. Pressure slowly bled off same as before. I cant seem to find a visual leak anywhere. What a pita this has turned to be. only thing in between is the fuel filter and I can easily see that its dry. Troubleshooting continues...