Ok, this has been driving my nuts. My fuel pressure only rises about 3 or 4 psi wot. I have a Cartech FMU from hahn (I know I know) The Vac source I have going to the 3rd nipple on the back of the intake mani, there is also a universal check valve in line to the fmu. It's set at 55 psi @ idle and I'm running 5psi of boost stock injectors. I just changed my fuel filter too. Also, I have a really crappy idle if I DONT have any fuel system cleaner in my tank. Anyone have any clues as to what this may be?

doesnt the check valve go after the fmu
i know when i had th cartech
the vacuum line went straight from the sourse to the nipple on the cartech and then a bleed line had the check valve
i never had a problem with mine

Originally posted by baxsom
doesnt the check valve go after the fmu i know when i had th cartech the vacuum line went straight from the sourse to the nipple on the cartech and then a bleed line had the check valve i never had a problem with mine

Yea x2. With a check valve, wont it not see positive pressure, therefor not raising your fuel pressure?

The hahn manual shows the check valve going between the manifold and the fmu so it can only see boost and not see a vaccum.

Do you have the check valve installed in the correct direction?

Originally posted by kasper6188
The hahn manual shows the check valve going between the manifold and the fmu so it can only see boost and not see a vaccum.

you got a manual??

by the time my manual was delivered the kit was almost on


check out this thread
it has a pic of my old cartech
you can see the check valve after the cartech and the car ran perfect

the only reason i got rid of it was i put in a portfueler with the aeromotive 1:1
idled at 45psi raised the pressure to more than double that at high boost



http://www.dsmtuners.com/forums/showthread.php?t=167703&highlight=cartech

Yeah, I have it installed so the boost can go through it to the fmu. I got my manual with my kit, got lucky. I'm going to try to do it like everyone else is doing it today though, just put it after the fmu. I hope this helps out because it's been doing this for a while now. I hope it's not my fuel pump. I have the 255lph that hahn supplies.

the inline? or did they start supplying intanks?

Hahn supplies the mini 255 intank now. The GSS 317. Its not the high volumn 255lph.

Terry