98 with running issue

[philv]

Hey guys, I'm working on my dad's 98 with 5.7. the truck sometimes will start and run normal and other times it'll start and die. It will even die while driving and sometimes it won't start at all. When it won't start you could wiggle the fuel pump relay and it would start. I hooked up a fuel gauge and koeo it registers 62psi and drops to 0 in roughly 3-4 sec. Koer the fuel pressure reads 54psi and sometimes it drops to 40, stumbles and dies. Then cycle the key and fires back up. What should be the first things to diagnose? I was thinking electrical, but with the pump dropping pressure I'm not really sure now.

 

[AllThrottleNoBottle]

Replace the relay and/or check the contacts in its socket. The relays do fail, so it wouldn't be crazy for that to be the issue...when it drops power for a second and truck's running, the pressure will fall off pretty quick as you described. Of course, if it's got the original pump or a ****-brand replacement, it's about time for it to give up the smoke, too...maybe you'll be lucky and just need that relay.

 

[philv]

I just replaced the relay and tightened the connectors for it. I noticed relay clicks on, I hear the pump, pressure is roughly 62psi. Relay clicks off, the pressure drops to 0 immediately. I'm thinking pressure regulator. Truck does start up a little faster when pedal is pressed while cranking.

 

[philv]

Just installed new fuel pump and truck now starts faster and system holds pressure when key is off.