Archived Lift pump oddities

[BadDNA]

I replaced the dead lift pump in my truck earlier this week and I've noticed some wierd behavior with the new one now. When I key on the truck the pump does not pressurize the system. I doesn't seem to start running until I start the engine. Once in a while it takes long enough to build pressure that the engine stalls before the fuel pressure comes up. I'm not sure how to troubleshoot this, the pump I put in is brand new, I've checked all my fittings and they're tight. I do need to replace the filter but I don't see any reason that would keep the pump from running. Once the pump does start it runs great, 14-16 at idle and 10 at WOT. Guesses, hints, offers to buy me a FASS are all appreciated.

 

[FourBarR]

you need to check the electrical connection at the pump. make sure its clean, contact cleaner, dialectric grease . make sure its plugged in solid. pump should run 20 to 30 sec. when key is turned on ,with engine not running. hope this helps.

 

[BadDNA]

I just read in another post where somebody suggested resetting the PCM by disconnecting the batteries. Has anybody had luck with that?

 

[nps]

The ECM controls the LP, not the PCM. So if you are trying to reset the PCM, I don't think it will make much difference.



One possibility is the LP relay in the PDC under the hood. Remove it and make sure it is making good contact.



An option is to bypass the ECM and run the LP off a relay. You can get an automotive relay from Radio Shack for about $5, mount it on the firewall, trigger the relay coil off a switched 12V line. Run a wire through an inline fuse from the battery to the relay contact. On the other side of the relay contacts, run a wire to your LP. When the key is on, the LP runs. Key OFF or on ACCY, the LP is off.

 

[Allnew2Me]

When I replaced mine a while back, it took a little driving to get the pump to pressurize when I turned the key to on. At first it didn't show on my gauge when I first turned on the key but the truck ran fine. That little short burst of pressure came on after I drove it a short distance. I had to bleed the air out of the lines at the VP and also a couple of injectors because it ran dry when the pump died. Try bleeding the air and it should start and run. Now mine gives the gauge a shot when I key on and comes right up to 15+ when running.

 

[BadDNA]

Okay, I reset the truck computer, bled the lines and buttoned it all back up this weekend. I still don't get any action from the pump when I key on, but if I bump the starter the lift pump will start running. I'm still not seeing any pressure though, it's like the system is losing it's prime overnight or when parked for any length of time. I can't find any leaks to speak of and I've retightened all the fittings just to be sure. This is really starting to become a problem for me, the truck is my daily driver. Any other suggestions? :{ I'm getting really close to biting the bullet and have Scott at MassDiesel drop a FASS pump in for me.