Fuel pressure dropping under boost

[Daily T/A]

Mods in the sig. My fuel pressure is dropping from 61 psi to 51 psi (6000 redline). Its a gradual drop as soon as I get into boost. I have the inline pump and 38lb injectors that comes along with the ati kit. I changed the fuel filter on saturday, looked underneath the car and couldn't find and loose hoses or anything. I've narrowed it down to either the inline failing, stock fuel pump failing, or a kink in the fuel line somewhere.

I also had a battery problem a month ago in which at idle voltage wise (13 ohms) everything was fine, but under load, it dropped to 3 ohms. So I replaced the battery.

Any advice appreciated,

Andy

[Teufel Hunden]

i'd recommend that you replace both your fuel pumps with one better one. Even though it usually works fine, i've never been a fan of the stock pump with a booster idea. On my car, i'm using the Walbro 255lph, and i've been very happy with it. You can usually find them for just over $110 or so. If you decide to go that route, be sure to check out the Fuel Pump Access Door instructions in the link i posted in the "How to" forum. Good luck!

[MIGHTYMOUSE]

take the belt off and make an n/a pass.. if it drops off then as well i would look into replacing the regulator.

[eboggs_jkvl]

That was my guess, FPR. It's not doing it's job.

I have a rising rate FPR. Every PSI of boost is 1 PSI of fuel pressure increase. Don't keep foolin around with lean under boost. It gets nasty on the engine fast.

E:)

[Pro Stock John]

Regulator or you need to change the intank pump.

10psi or greater drop is too much for any FI application.

[MIGHTYMOUSE]

i would say 5 is too much drop, and you have three times that much.

[eboggs_jkvl]

Originally posted by MIGHTYMOUSE
i would say 5 is too much drop, and you have three times that much.


Hey mouse, is Math yer strong suit? :D

[slow]

any drop is too much, imho ;)

my money is on the pumps not being able to support the fuel needs.

a regulator would cause problems more often then just the little bit of time your in boost.

Ryan

[MIGHTYMOUSE]

it was a trick statement. got ya!

10psi fuel pressure drop, then i assume he's running at least 5psi of boost which makes the relative pressure at the injector nozzle drop another 5psi.. = 15psi = (5*3)