kennebellgt

I have a 95 5.0 mustang mods in sig. my car has been running like crap some days it wont some days it does, when it does run like crap my fuel pressure gauge fluctuates from 30-25 sometimes a little farther and it flucuates really fast back and fourth like super fast i cant think for the life of me of what could be the problem i have a 98 cobra mustang fuel pump in it, i dont know if that would be the problem but list ideas thankyou

PRO50SC

25-30 psi is too low. Is the pressure normal when it's running well? If so, I would look into that.

samseed101

Yeah, that is a bit on the low side! First off, are you sure your gauge is working properly? Where is it connected? If it is working properly, then you can start trying to track down the problem. have you measured it with and without vacuum to the fuel pressure regulator? Does it change as the vacuum varies? And while we're on the topic, are you pulling enough vacuum? Of course, it could also be something like the pump, but why not start with the stuff you can check in a matter of seconds and takes minutes to replace.

15austin

Sounds like yer regulator is going bad.

Joel5.0

... '98 Cobra fuel pumps are "speed/pressure controlled" and have a "low speed" setting via a control module/resistor setup.

kennebellgt

so that could be my problem? and the fuel gauge is running off my fuel rail attached to a 1 foot fuel line hose, and when i take the vacuum line off it does change, what should i set my fuel pressure at with my mods? i have it set to 39 now it fluctuates the same just 39- 45 now