No fuel psi at key on

MyCARneedsHelp · Sep 15, 2005

Okay i know i been a bit of a nag about my cars problem but i finally bought a fuel pressure tester and i tested my buddys car and he gets psi at key on.... i dont... and then it goes up slowly when the car starts. I took it for a drive and the fuel psi goes down to 2-3 psi then she dies then the psi goes back up and it revives it self. Am i lookin at a fuel pump??? also when i turn the car off the psi drops right away. On my buddys 5.0 it holds..... what gives?

tunedin302 · Sep 15, 2005

May have a leak somewhere. Do you smell/see gas? Check around the injectors on the engine to see if the lower intake has fuel on it. Also, make sure your schrader valve is tight and nothing is causing the pressure to discahrge through there. When you turn the key do you hear the fuel pump kick on?

CoupedUp · Sep 15, 2005

Your pump has a check ball inside it that is supposed to delay pressure bleed-off when you shut 'er down.

To me it sounds like the pump is gone (2 hour swap in your driveway)
The only other thing I would double check before pulling it would be the voltage going into it.

If you look under your rear bumper and at the top of the fuel tank you will see a wiring harness running into the tank with a connector that can disconnect the harness. I would make sure you are receiving the appropriate 12 volts of power with the key on.

Fuel pumps are all about voltage and if you have corrosion or split or whatever in the wiring that creates resistance, then it's possible your pump is hardly getting enough voltage at all.

Good Luck, it's most likely the pump

HISSIN50 · Sep 15, 2005

The FPR can also be responsible for passing all the fuel back to the tank.

One can *CAREFULLY* crimp the return line to diagnose whether the pump FPR is at fault.
If you cycle the key several times before starting, does it start immediately and/or build pressure?
Good luck.

Swarzkopf · Sep 15, 2005

What fuel pressure regulator do you have?

Some brands (Aeromotive) bleed off pressure right away, so you wouldn't show any PSI with the car not running.

Euphoric306 · Sep 15, 2005

fuel filter may also be at fault, 6 bucks for replacement

MyCARneedsHelp · Sep 15, 2005

The pump,sock,strainer,filter,tank and fpr are all brand new out the box. Its just stock replacment... i get no psi at key on and when i start the car it slowly builds pressure it doesnt start until i get about 10 or so

CoupedUp · Sep 15, 2005

MyCARneedsHelp said:
The pump,sock,strainer,filter,tank and fpr are all brand new out the box. Its just stock replacment... i get no psi at key on and when i start the car it slowly builds pressure it doesnt start until i get about 10 or so

10 or so what ........ beers in you

HISSIN50 · Sep 15, 2005

Are you sure the gauge is good? I cant imagine the car starting or running worth a hoot on 10 PSI.

CoupedUp · Sep 15, 2005

MyCARneedsHelp said:
The pump,sock,strainer,filter,tank and fpr are all brand new out the box. Its just stock replacment... i get no psi at key on and when i start the car it slowly builds pressure it doesnt start until i get about 10 or so

"New" just means no body owned them before you, a shelved part can still be bad.
Why did you replace all of this and/or did you replace all of this to solve this problem and/or and/or?

MyCARneedsHelp · Sep 15, 2005

no not beers, as i turn the engine over the psi start to raise . The car starts at 10psi and continues to rasie as the car is running. It raises to about 30-32 psi. And yes i replaced all this crap to get this thing running right and its still not. The gauge isnt the problem i use it on every other vehicle and its fine.

MyCARneedsHelp · Sep 15, 2005

I also want to throw in there that i replaced the following things.... distributor,fpr,wires,cap,rotor,t.p.s,fuel pump, filter, strainer, sock, coil, solinoid, fuel pump relay, fuel injectors, battery, batter cables, inersia switch,pvc, 02 sensors and air temp sensor... geez this sucks, i havent been able to drive this car without it being stupid since i got it 6 months ago... i checked my timing a million times so i know its not that. Anything else to check replace? could it be a wiring issue?

HISSIN50 · Sep 15, 2005

What does cycling the key before cranking do? Do you get pressure?

If you pull codes and see a 95 or 96, that suggests the FP electronics are perhaps cutting out. This is not likely IMHO.

Good luck.

MyCARneedsHelp · Sep 15, 2005

no pressure when i cycle at all. And im not throwing any codes...

HISSIN50 · Sep 15, 2005

But the pump primes for 3-5 seconds with the KOEO? One can jump the ground terminal for the FP relay via the self tester if thinking it is an electronics issue (or probe the FP relay socket and note values).

The pump is likely bad, but using Fuel line crimpers can narrow down the pump vs the FPR (FPR is highly unlikely IMHO).

Good luck.

MyCARneedsHelp · Sep 15, 2005

yes the pump primes. There is no leak at the shrader valve eather. The pump was brand new from 50resto.com

MyCARneedsHelp · Sep 15, 2005

should i just take it to a local shop and have them do some diagnostic tests?? im lost i dunno what else to possibly check

HISSIN50 · Sep 15, 2005

Simply said, if the electronics and wiring are fine and you dont have pressure, it is very likely a bad pump. For what a shop would charge to diagnose it, you can probably buy another pump.

Good luck.

jrichker · Sep 16, 2005

Your year and mods are needed so I can post an answer to possible wiring/control problems. The wiring changed several times during the 86-95 years.

That's why it is a good idea to use the sig under the user control panel (User CP) option. It allows you to post your car year & mods, which help greatly when troubleshooting things. No, it is not there for us to snoop and see any "Secrets" you have hidden away under the hood. Be a good stangnetter and update you sig for future reference & don't keep us guessing.

spierce · Sep 16, 2005

I had the exact same problem TWICE!
Once it was the inertia switch.. check this first.. its in the trunk under the plastic right next to the driver side tail light.
the second time I had the problem was when I ran a NEW pump for about 3 weeks and the pump died! yea... it still primed but wouldn't start the car..
Replace the pump!
I paid 350 to get my wiring checked because I was convined it was not the pump since I just replaced it.. I even checked ALL the wiring myself but couldn't find anything..
It's going to be the pump..

No fuel psi at key on

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