Question about fuel pressure

[biggiesize]

I have a 99 Sport 4.0 sohc. When I turn the key I hear the fuel pump kick in for about 3 to 4 seconds. But when I go out to the engine and hit the pressure relief valve nothing happens. But if I get someone to crank the engine over fuel shoots out of the relief valve. Should I have pressure on the lines without the engine turning and just the fuel pump engaged?

 

[J_C]

Yes you should have pressure for at least a few minutes. Longer still except things start to leak as they get older.

Odd are that your in-tank fuel pressure regulator is bad, or an injector(s) are leaky. If you have a fuel rail dampener that might be leaky but I would expect that you'd notice the fuel smell when you went to check the valve.

Is it not starting or running properly? If the sending unit (includes pressure regulator) and pump are both original, I'd replace both while the tank is dropped, and a new fuel filter.

Then again there is a chance that not starting or running well could be some other problem and it has had a minor leak you didn't notice until this new problem presented itself.

 

[biggiesize]

Engine cranks but wont start.just stumbles occassionally.I put a new fuel pump in it 2 years ago with an autozone pump.Is there a test i can do on the fuel pressure sensor on the tank?

 

[J_C]

I'm not aware of any way to directly test the fuel pressure regulator in the tank, only to infer that it's probably bad if the pump seems to be working yet not holding pressure on the fuel rail, where you'd test with a standard fuel pressure gauge like you'd find as a loaner tool at autozone.

Then again, it's a 19 year old vehicle. If there were some rust causing a pinhole in the fuel line somewhere, or a leak at a fitting, that'll cause pressure loss too, but if it's a still day (no wind) I'd think you could look around the vehicle and smell a leak like that.

 

[koda2000]

The fuel hose from the pump to the regulator, or the regulator to the line can split or develop cracks. When you changed the fuel pump did you replace the 2 pieces of hose in the tank? If so, did you use submersible fuel line?

Also, as said, your FPR regulator may be worn out.