Well yesterday i finally got hold of a fuel pressure gauge and got it hooked up, at idle on a walbro 255lph HP, and a Vortech 12:1 FMU my fuel pressure is 53psi.I read it should be 43-50psi and i dont know how to get it down.I Took the FMU apart and it looks fine and i also fixed a vaccum leak on the FMU so it holds boost/vaccum now.I also cant get the fuel pressure over 73psi under boost.I tried sourcing the boost source for the FMU directly off the manifold to no avail.This has me stumped unless its a bad pump IDK what it could be.Filter is a few months old and i didnt find any leaks.Isnt there supposed to be a vaccum line on the stock FPR cause i dont see one.My MAP went bad yesterday too but im under the impression it only controls fuel injector pulse width and would have no direct affect on fuel pressure.

Thanks

Boostin'

anyone?

Boostin'

Most likely it's a bad pump.

You can't adjust the stock fuel pressure. Expect 55ish on a 96+ car. There is no vacuum line to the FPR except on 95's.

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Thats what i was thinking or a loose connector not allowing enough voltage to the pump. Guess ill check voltage and order a new 255 HP anyone got one for sale?Also my new map fixed that problem now i need to rewire my FCD since i took it off.If anyone else can think of a probable cause let me know.

Brian

Boostin'

Well i pinched off the return line to the tank today and pressure got to like 76psi.Im guessing the pump is bad or when i took the line loose from the feed when it bent a TINY bit is causing it, but i dont think that would cuase a 30psi pressure drop do you guys?Ill order a pump tommorrow and if that doesnt fix it i guess that Ill be looking for A FP housing for the late fuel system.Since the filter is only 3-4 months old i pretty much ruled that out, ill check voltage at the pump when i go to put the new one in.This is the only causes i could think of, how about you guys?

Boostin'

Alright the pump is bad.I ran a wire from battery to the pump directly.Also grounded it to the body and it only got 80psi and then the pump failed it started whining and Fuel pressure would go from 60-20 20-60 over and over.I think the pumps trying to lock up so i shut it off i'm gonna order one from extremepsi.Voltage with stock wiring was 11.4V. Voltage with a direct wire from the battery and a chassis ground was 12.56 volts source voltage.Also i did all this with 8psi applied to the FMU through a coolant pressure tester.Although no one is keeping up with this thread it should help anyone else having similar problems.

Boostin'

I'm keeping up with it, but I'm helping you through AIM haha.

Mike D
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Alright the new pump fixed my problem.It idles so smooth and maxes this 100psi gauge out at like 5psi.I get 53psi at idle.

5psi x 12psi=60psi rising rate
60psi+53psi=113psi Fuel pressure at 5psi

I can actually hear this pump humming at idle,and she is running like a champ.
Thanks guys.

Boostin'