ckyconan2003

iTrader: (2)

My car has had this issue and has been undrivable for the past month:

Random missfire code
Only 30PSI fuel pressure
all fuel pressure is lost after the key is turned off


I have replaced the fuel PUMP and REGULATOR and fuel filter......any ideas?

transam5.7lt1

iTrader: (18)

Oil pressure switch? also called oil sending unit....?

ckyconan2003

iTrader: (2)

fuel pressure not oil pressure

LT14MULAWS-6

iTrader: (2)

well right off the get go 30 psi is too low. at start up it should be somewhere around 45 psi and like 37 psi when its running. check gas lines, maybe something to do with the evap canister?? i doubt it though just somewhere to look that might directly affect fuel pressure.

Ralls

iTrader: (32)

Does it blow blue smoke out the tailpipe when first starts up?

LT1Falcon

iTrader: (3)

how does it run when its on? possibly bad injectors, if one was stuck open it might make the pressure drop and make it misfire, dont know from experience but sounds like a possiblility

ckyconan2003

iTrader: (2)

Evap canister eh?

How do i test that?

Camaro_freak

iTrader: (1)

I don't see how it could be the evap canister since there are no pressurized fuel lines there. Maybe a stuck open injector as someone else mentioned, but I don't think that would drop your fuel pressure to 30. Maybe a bad wire to the fuel pump?

ckyconan2003

iTrader: (2)

I have replaced the pump once with a Delphi pump. I am banking on the chance that it may have been a bad lemon out of the box, ima order another one tomorro and try that. However if it doesnt work with the new fuel regulator ima hit something.....really really hard

buffman

iTrader: (9)

pull the fuel rail and turn the key on to pressurize the fuel system. Inspect the injectors to make sure one is not faulty..

ckyconan2003

iTrader: (2)

Is there any way to look at the relay and tell if its broken? I thought that the relay either worked or it didnt since all it does is deliver electricity to the pump

LT14MULAWS-6

iTrader: (2)

ya i could almosst go with a bad injector being that u have a random missfire code that can be the fault of the injectors

transam5.7lt1

iTrader: (18)

I said oil pressure switch because the fuel pump does get a reading from the oil sending unit, if you have a faulty oil pressure switch, sending a false signal of low oil pressure, it will cut off fuel pump pressure..... now.... does it make more sense to you?????

buffman

iTrader: (9)

^^ actually I dont think it works that way. I recall the oil pressure sending unit will allow the fuel pump to continue to be powered if it blows the fuse and the car still sees the car has oil pressure.

transam5.7lt1

iTrader: (18)

I understand that it will cut off fuel pump if oil pressure is too low in order to avoid any damage to the engine. So, if its sending a false signal, or if its leaking, it will trigger such action. We fixed a friends car that had a similar problem, he replaced a bunch of stuff, such as fuel pump, relay, opti, module, coil... still his car wouldn't run for too long... untill he replaced the oil sending unit... I am just telling my expierience on a similar situation.

buffman

iTrader: (9)

^^ maybe it's different on the f-cars, cause it doesnt work that way on the bcars. You can unplug the darn oil pressure sending unit, get the light to show up on the dash, and it will still run..

jester1

iTrader: (1)

fuel pressure is controlled by the regulator. when you turn the engine off vacum goes to zero which closes the return line. There is a checkvalve in the fuel pump to keep pressure in the rail for the next start up.
Either you have a faulty checkvavle, failed regulator, or leaking injector (s).
you should check the vacum line that attaches to the regulator and see if there is any trace of fuel.
its not electrical so keep your test light in the tool box.

Low N Slow

iTrader: (4)

I had a similar problem with mine, it ended up being a small hole in the fuel line that runs from the pump to the metal lines in the tank. I found it by pressurizing the pump with it out of the car.

moserman

iTrader: (7)

change the fuel filter along the underside of the car

Arkanzan Wheeler

Did you ever figure out the problem? My car is doing the exact same thing now and I have replaced everything I could think of...