i bought a car to fix up, built the motor put everything back to together started right up idle fine, problem is this, i am running an sfmu with the 2.72 disc and dark spring with 440cc injectors. i get the car to start and idle fine, but when i rev it, the car dies and bogs down, so i reved it in the engine bay and watched the f.p gauge and when i rev the car the fuel pressure drops quickly and goes down to zero and then when i let off the gas it goes back to its idle pressure, why is this......oh just a fyi i am running a walbro 22lph high pressure. could it be the settings on the sfmu or do i have the wrong spring in what could it be.



Mods:
CAI, OBX exhaust, Grillcraft grills, altezzas, ard ryver g6 17's wrapped w/ falken's, VIS racing c.f hood, 2 12" kicker comp's w/pioneer h.u, streetglow blue undercars, red dash kit, indiglo guages, n other shit

whats ur idle fp set at ? also you might need a bigger fuel pump then 22 lph

i meant 255lph h.p walbro also my idle fp is abount 20psi



Mods:
CAI, OBX exhaust, Grillcraft grills, altezzas, ard ryver g6 17's wrapped w/ falken's, VIS racing c.f hood, 2 12" kicker comp's w/pioneer h.u, streetglow blue undercars, red dash kit, indiglo guages, n other shit

i am really stumped what would cause me to lose fuel pressure whenever i rev the car, i even disconnected the vac line to the sfmu and just plugged it comming out of the manifold and lost fuel pressure so it cant have anything to do with the sfmu, also i am 99 percent sure there arent any fuel leaks. what could it possible be?



Mods:
CAI, OBX exhaust, Grillcraft grills, altezzas, ard ryver g6 17's wrapped w/ falken's, VIS racing c.f hood, 2 12" kicker comp's w/pioneer h.u, streetglow blue undercars, red dash kit, indiglo guages, n other shit

the ecu turns off the injectors when you let off the gas .if you had a widband you would see it spike to 21 everytime . it shouldnt cause it to stall tho

no that is not the problem the problem is, when i rev the car, while the revs are climbing my fuel pressure steadily falls and my car cuts out when it gets to low, i am wondering why my car is dropping fuel pressure when it should really be rising



Mods:
CAI, OBX exhaust, Grillcraft grills, altezzas, ard ryver g6 17's wrapped w/ falken's, VIS racing c.f hood, 2 12" kicker comp's w/pioneer h.u, streetglow blue undercars, red dash kit, indiglo guages, n other shit

your fuel pressure drops because when you rev your engine your injectors are lowering the pressure by useing the fuel up that is in your fuel line and rail. i have the same setup(sfmu,440,ect). i had alot of trouble with this too. i sounds like your fuel filter is not flowing enough fuel. i put a brand new (stock)filter on, same thing,poked a hole in it and it was all better. i got a better filter now that was just a test. also another huge problem with any 420a is the fuel rail itself. let your car sit for even for a few days and the inside of your steel rail will be full of rust. then every time you go to raise the pressure(rev it up) you clog not only your injectors but your pressure gauge so you get a false reading. i now have high flow filter,3/8 fuel line from tank to rail, and obx fuel rail(junk by the way)and everything is better but look towards you filter and rail. p.s. might want to check you voltage right at the pump to.

i figured out the problem with this already, it was that my line was clogged, not fully but enough that the injectors would flow more fuel than the clog would so i would have to wait for the rail to fill back up, ran a new line and bamm fuel pressure again.




Mods:
CAI, OBX exhaust, Grillcraft grills, altezzas, ard ryver g6 17's wrapped w/ falken's, VIS racing c.f hood, 2 12" kicker comp's w/pioneer h.u, streetglow blue undercars, red dash kit, indiglo guages, n other shit

Originally posted by mike rs-t
another huge problem with any 420a is the fuel rail itself. let your car sit for even for a few days and the inside of your steel rail will be full of rust.

FWIW, i have *never* seen internal rust in a 420A fuel rail.