low fuel pressure

[btrucker07]

i have a 2000 cummins all stock other than the lift pump put a aftermarket stock replacement fass one on the last few days i cant get fuel pressure ill hit the key and i can hear the left pump run for the aloted time ill start the truck pressure will go to 12 then slowly drop to 0 i shut the truck off and bump the key again i dont hear the lift pump running went to the stor and bought power service 911 dumoed it in and reran truck pressure went from 8 to 5 then slowly climbed back to 15 psi drover truck around seems great but when i put a heavy fuel demand on it my pressure drops from 12 to 8 and truck feels like it falls right on its face is this a sign that i should just replace my feed pump?

[mountianman69]

Have replaced your fuel filter to make sure it is not cloged?

[ncsucarjock88]

Have you changed the filter on the FASS??

I'd certainly check that first.

[btrucker07]

yep not even a week old

[Mopar1973Man]

Air Leak?

Low of fuel?

Regulator problem?

[btrucker07]

you talkin the inline filter they give you when i bought the pump right. if you are no i have not