Fuel Pressure Problem

93White5.0Conv · Jul 30, 2004

I have been having some long cranking times when starting my 93. It will start it just sometimes takes a while to do it. It runs fine except the idle is a little rough.

I just checked the fuel pressure and when I turn on the key but do not start the engine it is 38 psi which is ok. The problem is that most of the time after about a second or two the pressure will drop to 0! Sometimes it will stay at 38 psi. I start the engine and it is at 33 psi which is ok. I shut the engine off and it stays pressurized without dropping for several minutes at least (I quit checking after a few minutes.)

Does anyone know what is wrong? Where is the fuel going to? I know that this is not normal because of reading Charles Probst "Ford Fuel Injection & Electronic Engine Control." I had another problem several years ago that I measured the fuel pressure when trying to solve it and the pressure never drop to zero. Check valve in fuel pump? Fuel pressure regulator?

willys1 · Jul 30, 2004

93White5.0Conv said:
I have been having some long cranking times when starting my 93. It will start it just sometimes takes a while to do it. It runs fine except the idle is a little rough.

I just checked the fuel pressure and when I turn on the key but do not start the engine it is 38 psi which is ok. The problem is that most of the time after about a second or two the pressure will drop to 0! Sometimes it will stay at 38 psi. I start the engine and it is at 33 psi which is ok. I shut the engine off and it stays pressurized without dropping for several minutes at least (I quit checking after a few minutes.)

Does anyone know what is wrong? Where is the fuel going to? I know that this is not normal because of reading Charles Probst "Ford Fuel Injection & Electronic Engine Control." I had another problem several years ago that I measured the fuel pressure when trying to solve it and the pressure never drop to zero. Check valve in fuel pump? Fuel pressure regulator?

Actually it is normal for the fuel line to keep pressure after you turn it off.(Its a sealed system)Pressure will stay in it for 30--45 minutes.When you first turn the key on,the pump is priming the system so it will read higher till the pump stops,then it will drop a little.

93White5.0Conv · Jul 30, 2004

willys1 said:
Actually it is normal for the fuel line to keep pressure after you turn it off.(Its a sealed system)Pressure will stay in it for 30--45 minutes.When you first turn the key on,the pump is priming the system so it will read higher till the pump stops,then it will drop a little.

I understand that is normal for the fuel lines to keep pressure after I turn it off. The problem is when I turn the key on I get the correct pressure (38 psi.) but after 1 to 2 seconds the pressure all bleeds away to zero most of the time. It sometimes stays pressurized like it should but most of the time the pressure build up when the fuel pump turned on goes away.

HISSIN50 · Jul 30, 2004

it could be the check valve in the pump is halfway bad. what happens if you prime the pump a couple times and then check pressure (like you do now, when it shows 0 psi)?

93White5.0Conv · Jul 30, 2004

HISSIN50 said:
it could be the check valve in the pump is halfway bad. what happens if you prime the pump a couple times and then check pressure (like you do now, when it shows 0 psi)?

I just tried it again. Each time I turn the key on the pressure goes up to 38-40 psi. Then it either drops quickly to zero (1 second) or slower (5 to 10 seconds). When I tried it earlier this evening it would sometimes stay at 38 psi.

If the check valve in the fuel pump is bad what problems would I have with the car until I replace the fuel pump? Just hard starting? Or more problems?

HISSIN50 · Jul 31, 2004

93White5.0Conv said:
If the check valve in the fuel pump is bad what problems would I have with the car until I replace the fuel pump? Just hard starting? Or more problems?

generally, as you said, hard starting for some people. some guys say they have to crank it for a bit longer to get it to catch - others dont (depends on how big a pump you run too). that is weird that even if you cycle the key (mulitple primes), it drops to nada.
are you sure the gauge is giving a good reading?

this is really weird. good luck and bump.

93White5.0Conv · Jul 31, 2004

HISSIN50 said:
generally, as you said, hard starting for some people. some guys say they have to crank it for a bit longer to get it to catch - others dont (depends on how big a pump you run too). that is weird that even if you cycle the key (mulitple primes), it drops to nada.
are you sure the gauge is giving a good reading?

this is really weird. good luck and bump.

I still have the stock pump at 126K so it is just 88 LPH. I have experienced the hard starting / longer cranking recently. I do not need to every time just some of the time.

I believe the gauge is giving me a good reading. It stays at 33 psi when running at idle.

Thanks for the help!

Fuel Pressure Problem

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