I have a 98 GMC K2500 with 5.7L. I have put a new fuel pump on back in June 08. That was the second pump that month with the first one loosing pressure enough that I had no power going down the road and hard to start. This pump did good for a few months but now is very hard to start. Put a fuel pressure guage on and have pressure while running but let it sit over night and it goes to zreo. Could this be another bad pump or maybe bad fuel pressure regulator or could it be something else? Need suggestions bad.

 

You need to pinch the return line closed and see what happens. How quickly does the pressure fall? Did you do the filter at the same time?

 

How and where would you pinch the line without messing it up? I also checked the pressure after starting and had 60 psi. After sitting 1 hr it dropped 16 psi.

 

Whatever my problem is it is not consistant. After loosing the 16psi it sat for another 24hrs and did not loose anymore pressure. Any suggestions would be appreciated.

 

Any where it is rubber. I think there is a rubber section of return and pressure where the line come off the trans 2 the filter. You need to use hose pinch off pliers or smooth teeth vice grips. It is normal for FP to fall off some. However you should not be able to watch it drop instantly as soon as you turn off key. Intial it should go up slightly