KillSwitchNY

My cars specs are listed below. but i have a 255LPH fuel pump that was done about a year ago witha new fuel filter. i have a fuel pressure guage so i know how im running. but since i can remember the guage will rattle rapidlybetween 30psi-40psi even when driving it is unsteady. This is both with or without a full tank of gas. Yet some days the pressure will be perfectly level and steady. and the car will run great. Any idea what this could be? its been going on and off for so long its so irritating. please help

BTW :Myfuel pressureregulator is set to 38psi

Colorado_Mustang

First question is whether you havea returnless style system or not. They are known to give inconsistant pressure without a fuel control computer.

It could simply be your gauge. A bad ground or sender contact will definitely provide the readings you're seeing. I'd check that first.

KillSwitchNY

what do you mean? a bad ground where?? inside the guage itself? because its a simple unit. its a saleen guage the screwed into the schrader valve on the fuel rail. thats it. I was also thinking it may be a bad guage but sh*t the guages i have a rare and super hard to find.

Colorado_Mustang

Thought you'd have that gauge mounted inside the car through a sender. I have an engine mounted fuel pressure gauge as well and they aren't reliable after the engine is warmed up due to how the gauge is built (sealed and liquid filled...alters the pressure reference).

Yours could be as simple as the valve not being pressed all the way down by the gauge.

BTW, how are reading the gauge while driving if it's mounted in your engine bay?

KillSwitchNY

haha, it takes skill!! no, i meant its mounted inside the car. yes i know, you dont have to lecture about how unsafe that is. lol, but its because its how i got the car. with a center A/C vent gauge plate.

Colorado_Mustang

I'd go ahead and replace it with an electronic gauge. You could be just seeing some issues that that style gauge has with the tubing distance. If the pressure was really changing that much, the engine would change how it runs. I went through a similar problem when my gauge would show 0 psi for fuel pressure, but I would still have no problem hitting 7k rpm.

KillSwitchNY

i hear ya.. but i really dont want to give up that saleen guage .... i gotta try and pull it out and fix it if thats the problem. because some days it will be perfectly steady and accurate