06 F250 Erratic Fuel Pressure

[PowerSToKed]

Vehicle has a new fuel pump, secondary fuel filter and pressure regulator, at idle fuel pressure fluctuates between 60 and 70 psi (checking at pump) fluctuation seems excessive, concern is very intermittent but while driving fuel pressure will drop to 0psi, I have checked for an inlet restriction during the concern as well as power and ground to pump NPF, Anyone seen anything like this, maybe combustion gas? vehicle does not skip until the loss of fuel pressure

[cbriggs]

Can you pull a fuel sample when the pressure drops off? Possibly a pinhole in a fuel line or a problem with the sending unit causing fuel aeration. See if sample is really foamy.

[deezul]

How much fuel is in the tank when the concern occurs?? I had an issue similar to this, this past summer where it was the pickup tube in the tank. I never had fluctuating pressure until 1/4 tank and less. The truck would perform excellent until 1/4 tank reached, after that fuel pressure would be extremely erratic as well as driveability concerns. The pickup in the tank had a crack in it allowing it to suck air from time to time.

[Mekanik]

How much fuel is in the tank when the concern occurs?? I had an issue similar to this, this past summer where it was the pickup tube in the tank. I never had fluctuating pressure until 1/4 tank and less. The truck would perform excellent until 1/4 tank reached, after that fuel pressure would be extremely erratic as well as driveability concerns. The pickup in the tank had a crack in it allowing it to suck air from time to time.

I've had one of theese too. It seemed like the right bank was affected first.

[deezul]

I've had one of theese too. It seemed like the right bank was affected first.

Agreed. Everytime it sucked air cylinder #1 would drop off on power balance.

[Keith Browning]

Which makes absolutely no sense considering both heads are fed from the filter standpipe and both fittings for the heads are the same depth from the top of the filter housing. ( I measured)

[Mekanik]

I don't know why either. I'll tell you this though, the first one I had like this I replaced injector O-rings on the right bank. Then I had someone put fuel in the truck so I could drive it home. I thought it was a 'confirmed kill' because it didn't skip a beat. I temporarily fixed the truck by having someone put fuel in it. Imagine how I felt when it came back.

 

To actually fix this particular truck I made two clear tubes; one to go in-line with the fuel supply before the pump, and one in the return line.