Fuel Pressure Problems
Thread Starter
Instructor
Joined: May 2012
Posts: 210
Likes: 2
From: So. Ill. Ill
Fuel Pressure Problems
I have a 2005 C6 with a built 402 and a upp twin kit on it with the upp fuel system plus all the supporting stuff. To understand my problem you will need to know how the system works. I have the stock pump feeding the stock rails with a whole drilled in the drivers side tank hooked to a -6 an line running to a boost activated walbro 255 pump which hooks to a non boost referenced regulator at 58psi, which feeds the acess port on the stock rail. My problem is that my fuel pressure is all over the place. It was fine for a few days when I got the car back this last time and now it is all screwy. So i will start the car and have 58-60 psi then go driving for a while and the pressure will stay perfect. Ill stop somewhere for a little bit, start the car back up and pressure is anywhere from 48-55psi (at this point time I'm freaking out). So go driving for a bit at the low pressure and after a mile or two pressure goes back up to 58-61psi. So I talked to a friend and he said try blocking my secondary system off to see if the pressure is not bleeding through it. I try'd this and still the same issue. So I am running out of ideas, and if anybody has any ideas I would be grateful.
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
Have you talked to CK? The system design is different than any other fuel system I've seen. Could be the stock pump backflowing through the secondary regulator if I were to take a SWAG.
Thread Starter
Instructor
Joined: May 2012
Posts: 210
Likes: 2
From: So. Ill. Ill
I thought the check valve could be failing on the secondary regulator so i blocked the whole second system off and just cruised around on the primary and still had pressure fluctuations. I haven't tried putting a mechanical gauge on it though.
Former Vendor
Joined: Jan 2011
Posts: 1,116
Likes: 39
From: Colorado Springs CO
What is the pressure on the secondary system set at? Disconnect it from the rail and plug it, then activate the secondary system. If it's too high, it's possible that it damaged the factory reg.
#2: how accurate is your gauge? Check your log files and watch the STFT see if it's fluctuating consistently with the fuel pressure.
This is one reason we designed our system completely stand alone and dormant, so it would play no effect in the factory fuel pressure under "normal" driving conditions.
If you do find an issue with your stock reg, it may be best to remove it, then take out the check valve on our fuel system and run it as a full return style (then you can even boost ref it!).
CK
#2: how accurate is your gauge? Check your log files and watch the STFT see if it's fluctuating consistently with the fuel pressure.
This is one reason we designed our system completely stand alone and dormant, so it would play no effect in the factory fuel pressure under "normal" driving conditions.
If you do find an issue with your stock reg, it may be best to remove it, then take out the check valve on our fuel system and run it as a full return style (then you can even boost ref it!).
CK
