fuel delivery problem
Thread Starter
Drifting
Joined: May 2005
Posts: 1,258
Likes: 38
From: springtown Texas
fuel delivery problem
when i was at the track 2 weeks ago my GS was surging at the top of 3rd and wouldn't pull past 5000 rpm in 4th.
well i finally had time today to put my fuel pressure gauge on it and see what its doing.
i had the pressure set at 40psi, today when i checked it it was at 38psi.
as soon as i touch the throttle it jumps up to @42 then falls back. so i stomped it and it jumps up for a split second then drops to @35 psi. if i hold it at 3000 or 4000 it falls to @35psi and stays there then goes back to @38 at idle.
when i take the vac line off it goes to @41 psi and stays within 40-41 psi no matter what i do, rev it or hold it at any rpm.
does this sound like the regulater is bad or maybe the fuel pump.
it has an aftermarket fuel pump in the tank and an ajustible fuel pressure regulator. what brands are they i have no idea, they were on the car when i bought it.
anyone ever have this problem.
well i finally had time today to put my fuel pressure gauge on it and see what its doing.
i had the pressure set at 40psi, today when i checked it it was at 38psi.
as soon as i touch the throttle it jumps up to @42 then falls back. so i stomped it and it jumps up for a split second then drops to @35 psi. if i hold it at 3000 or 4000 it falls to @35psi and stays there then goes back to @38 at idle.
when i take the vac line off it goes to @41 psi and stays within 40-41 psi no matter what i do, rev it or hold it at any rpm.
does this sound like the regulater is bad or maybe the fuel pump.
it has an aftermarket fuel pump in the tank and an ajustible fuel pressure regulator. what brands are they i have no idea, they were on the car when i bought it.
anyone ever have this problem.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
regulator
The spring in the regulator is supposed to react to the fuel that is pushing at the diaphragm. The regulator sounds like it's working, but that the spring may have lost it's ability to counteract high vacuum and constant fuel pressure at sustained RPM.
I would put a new spring in the regulator, and try that.
The spring is like a balance fulcrum against the fuel pressure introduced on one side, and the vacuum is the lever on the other side that adjusts the amount of fuel that dumps in the bypass hole to return to the tank.
If you use just the spring, no vacuum, it should jump from 38-40 to 45.
If the spring is weak, and allows more bypass, it will only go to your 41.
just my 2C
Chris
I would put a new spring in the regulator, and try that.
The spring is like a balance fulcrum against the fuel pressure introduced on one side, and the vacuum is the lever on the other side that adjusts the amount of fuel that dumps in the bypass hole to return to the tank.
If you use just the spring, no vacuum, it should jump from 38-40 to 45.
If the spring is weak, and allows more bypass, it will only go to your 41.
just my 2C
Chris
Last edited by coupeguy2001; Mar 24, 2007 at 12:31 AM. Reason: added clarification
