Hi guys,

I've had a tough time finding every specification for my fuel pressure. The truck is a 2000 f150 xlt, originally a 4.6. I swapped in a 1997 5.4 engine.

-My running pressure is 30 psi idling and goes up with RPM

-Removing vacuum from the fuel reg pressure rises to 40 psi

-My key on engine off pressure is around 35 psi but drops down to 25 in less than 10 seconds. If I leave the key on for a minute and try to start I have a hard starting condition. I need to cycle the key off and on before starting to make it easier.

The truck runs alright but I think it could be better. Is this fuel pressure leakdown affecting anything other than starting? How do I find what is wrong without senselessly replacing the fuel reg ($130 from ford) or the fuel pump.? Thanks

 

I did some reading somewhere and found that there is some check valve type thing on the fuel pump that stops pressure from leaking down. I've done a lot of off roading and driving fast over rugged terrain, that will apparently break or render that feature of the fuel pump useless. Its been like that for a while now and ill just keep driving it til it goes.

 

Most vehicles run at around 50-60 psi, if the pressure is dropping off too much after shut off then that would cause a hard start, sine it's only running around 35 u deff have low fuel pressure and could be as simple as a bad pump or pressure bleeding off somewhere In fuel delivery system

 

Bleeding down 10# in such a short time and no obvious fuel leaks, then you most likely have a fuel pump issue. Your description of your problems make me think you have a weak fuel pump. Oh yeah, if you do have to replace the pump, order one for the 5.4 for your engine year, to get the right pressure reading. They may be the same, but I believe there is a different part number. Nope, just checked. Same pump for 97 and 2000 with the engine combo you have switched.

 

Had the same problem about 4 months ago. I had the same readings key on, engine off. Quick pressure leak down when engine off. Replaced the pump with Bosch. Fixed my starting problem. Removed the bed of truck to replace pump. Can be done without helpers.
Let me know if you need more help,
John

 

Thanks guys, I think i have a weak pump. I changed fuel filter at its regular interval and felt a significant improvement in performance even though the old one was not that bad. I noticed a small leak from an injector o-ring when I changed the plugs out. I replaced all the o-rings and the pintle caps and felt another significant improvement. I think my pump is very sensitive to these small issues and if I want to get the best performance (and I do) I will change pump