Engine/Transmission (1998.5 - 2002) LiftPump, Again?

[Mel Swanson]

Shortly after I installed a Westtech fuel pressure Gage from Geno's my fuel pressure dropped to 3psi (32K miles). Installed a new Carter lift pump obtained from the local truck shop. At the same time I installed the so called fix of all fixes,WildCat Diesel , banjo eliminator kit.



Now at 44K miles the pressure gauge is giving me odd readings, i. e. , 14psi will drop to 10 or 5psi and hold. If I put my foot in it the psi will bump back up and sometime go all the way to 15psi. At times it will ride at 8 or 9 psi for miles and drop to 3psi. A heavy foot will bring it back up to around 10 or 12psi. Very inconsistent. the wires to the sending unit and gouge seam to be ok.

what does the experience say?

DO I NEED A NEW LIFT PUMP?

 

[Gary - K7GLD]

Sounds like a defective/erratic internal bypass valve in the LP - I'd get a new one and keep the current one as an emergency spare...

 

[majasride]

Exact same thing happened to my truck last week , parked it until I could pull the lift pump , and returned it to cummins for a new one . They have a one year warranty . Works fine again now ,hope I get another six months out this one.

 

[isb360]

I recently replaced the lift pump in mine and in the last week or two notice the idle fuel pressure drop suddenly from 14psi (normal idle psi for me) to about 10psi, but if I put my foot on the throttle, it pops back up to where it should be.



If I had an electric FP gauge, I'd think it was that, but the mechanical gauge rules that out.



Tell me a bit about the bypass valve in the LP.



Could that be it?



Thanks

Tim

 

[Mel Swanson]

isb360



I do not know anything about a bypass valve in the LP. Guess that could be it. Please tell me more.

 

[isb360]

Gary - KJ6Q



Can you tell me more about the internal LP bypass valve, it's function, and what effect it might have if it is faulty?



At very light/no throttle, my FP jumps from 9psi to 14psi, as if something was opening and closing erratically. Under any load, however, the pressure steadies at 13psi and, of course, pulls down in response to throttle input.



Thanks in advance.

Tim