Fuel pressure bleeds off.....help

ninety15.0 · Aug 8, 2005

So i just finished up putting the motor in my car and fired it up for the first time...it started on the first turn and ran for about 2 seconds and died out. I noticed that when i would prime the fuel pump the pressure would jump up to just over 40 but almost immediately lost pressure and in about ten seconds it was reading 0. I checked all the injectors and nothing was leaking either at the manifold or the rail.... Im thinkin that i may have the vac lines routed wrong for the adj fuel pressure regulator and for some reason not letting fuel get to the motor? Is that possible? i changed to an explorer intake and am still unsure what to do with some of the vac connections. any help would be appeciated.

Nick

BLOWN 5.0 FOX · Aug 8, 2005

do you have an electric or mechanical gauge? I had a mechanical -liquid filled gauge mounted on my fuel rail and it also bled off after the engine was shut off. Now I have an electric Autometer gauge and it holds pressure.

ninety15.0 · Aug 8, 2005

Its a mechanical guage mounted at the end of the fuel rail...before i took the motor out when i primed the fuel pump the pressure would stay at 40 for like twenty minutes...where could i be losing pressure from?

HISSIN50 · Aug 8, 2005

A bad pump or FPR can cause an issue like this, as can bad FP electronics (worth noting if you retrieve codes).

Are you sure the FP stays on after the car starts?

Good luck.

vristang · Aug 8, 2005

I had the exact same thing happen to me just a couple of weeks ago when I started up the 408. Very long story made very short, I replaced the fuel filter.

After that, the pressure held just fine. Can anyone explain this? I didn't think there would be an anti-drainback valve in the filter, just in the pump/tank.
I had a cheapo Fram in before (it was new and had not been started), and replaced it with another Fram. The car had been sitting for about 8mo.

I can't explain it, but maybe it will help you out Ninety15.0

ninety15.0 · Aug 9, 2005

Yea my car has been sitting for about nine months...it had about a 1/4 tank of gas with a thing of stabilizer in there. I put five gallons of good gas in before i started it. The pressure bleeds off so fast it seems as though theres a major leak in the fuel system....but no drips that i can see....any help would be appreciated

ninety15.0 · Aug 9, 2005

Oh yea....due to an h-pipe problem i am starting the car with open headers and no O2's....is this going to be a major problem?

CManT1914 · Aug 9, 2005

ninety15.0 said:
Oh yea....due to an h-pipe problem i am starting the car with open headers and no O2's....is this going to be a major problem?

No problems as long as you don't run it too long like this or rev it.

As for the fuel pressure thing, ever since my BBK afpr went on, my fuel pressure jumps to 40psi when I turn on the key, then slowly lowers to 15 psi. I'm not worried about it since there are no leaks anywhere, and it holds pressure just fine while running.

HISSIN50 · Aug 9, 2005

One can use a fuel line crimp tool to carefully crimp the return line. If the pressure goes up, the FPR is like me after mexican food (passing too much gas).

If the pressure does not go up, that suggests a weak pump and/or pump check valve (depending upon how you do the test).

Good luck.

ninety15.0 · Aug 9, 2005

I dont think the car held FP when it was running....i would prime the pump and the press would jump up to 40 like normal and then when i turned it over it would start up and the pressure would drop to zero and it would die...? im thinkin it may not be a fuel problem...could a crappy engine ground do this? Can i rule out the vacuum problem, or could that be causing problems getting the car to run? thanks a lot

CManT1914 · Aug 9, 2005

HISSIN50 said:
One can use a fuel line crimp tool to carefully crimp the return line. If the pressure goes up, the FPR is like me after mexican food (passing too much gas).

ROFLMAO

ninety15.0 said:
I dont think the car held FP when it was running....i would prime the pump and the press would jump up to 40 like normal and then when i turned it over it would start up and the pressure would drop to zero and it would die...? im thinkin it may not be a fuel problem...could a crappy engine ground do this? Can i rule out the vacuum problem, or could that be causing problems getting the car to run? thanks a lot

I would think that might be a weak pump. It primes it, but when it needs to constantly supply fuel, it just can't keep up. A vacuum leak would cause other problems too, so I doubt it's that, although I could be wrong...

HISSIN50 · Aug 9, 2005

Chris is right. Toss a gauge on and watch it when it primes and while it runs. If it is below 30 PSI for any amount of time, something is up. As said, it can be the FPR returning too much fuel to the tank, or a weak pump. See above test to diagnose further.

Have you pulled codes? Code 95/96 have to do with fuel pump electronics.

If you had the vac line off the FPR, pressure would go up, which only helps. Probably not the issue.
Just watching a gauge for a bit is the place to begin and only takes a couple mins.
Good luck.

ninety15.0 · Aug 9, 2005

Ima go out there now and try and get it runnin....i will check back later thanks for the help

ninety15.0 · Aug 9, 2005

Well i replaced one injector and replaced the fuel filter and that seems to take care of the fuel delivery problems....but now i just cant keep it running. It starts and revs up to like 16-1700 liek normal and then comes down to like 5-600 and tries to idle and dies. It smells really rich and flames shoot out the headers when it stalls or when you try to give it gas....im stumped

vristang · Aug 9, 2005

ninety15.0 said:
Well i replaced one injector and replaced the fuel filter and that seems to take care of the fuel delivery problems....but now i just cant keep it running. It starts and revs up to like 16-1700 liek normal and then comes down to like 5-600 and tries to idle and dies. It smells really rich and flames shoot out the headers when it stalls or when you try to give it gas....im stumped

I'm glad the filter worked for you, even if I don't understand why it worked.

If you are still not using the O2 sensors now might be a good time to get those things installed. Without them you really have no chance of getting a good fuel mixture.

Then again some have had problems with the mixture even with O2s in place.

Fuel pressure bleeds off.....help

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