I have a 97 F-250 with 7.5L 191,000 and some change for miles and dual tanks and I have been thinking I have had some fuel pressure problems. I hooked up a fuel pressure gauge to the rail and with the key on and engine off I have zero fuel pressure. After sitting over night and I go to start the pickup it cranks and cranks and cranks and then will eventually come to life. Fuel pressure with engine running is 30 PSI which is on the low side of the spec. After the truck starts and shuts off the fuel pressure holds good for a long time so I suspect my check valves are all good and I don't have any issues with fuel transfering from one tank to the other and when I go to re-start it fires right up.

1. Why do I have zero fuel pressure with key on engine off but have fuel pressure with engine running?

2. Has any one ever tried to just replace the fuel pump with in the FDM? I see the whole thing is close to 500 bucks and with two tanks I dont know if I want to drop that kind of money when I could replace both pumps for a fraction of that.

3. Other wise the pickup seems to run good on the rear tank, front tank it sputters and dies. The fuel pressure does move around a lot more with the front tank but overall stays close to the 30 psi.

Any ideas or suggestions would be greatly appreciated!

Jeff

 

Interesting, I'm surprised she starts. Try doing another engine off test by jumping #2 to #6 for fuel pump continuous run pressure Ford Fuel Injection » How To Run a Self-Test test.

oops, just noticed your year truck

 

Fuel pressure sounds about right.
I take it you have an OBD-1 truck so doing the jumper pin #2 to pin #6 of the self-test plug under the hood should work with the key on and engine not running.

Not running well on the front tank could be a problem with either FDM in the front or back tank.

The FDM cost about $150.00 at most auto part stores but you do not get the hanger or the fuel gauge sending unit.

It may be flooded as to why it does not start after sitting over night. Try holding it on the floor and see if it starts right up if so you may have leaking injector(s).
Also pull the vacuum hose off the nipple of the Fuel Pressure Regulator (FPR) and turn the key on and off with a cold engine and see if fuel comes out of the nipple on top of the FPR. If it does it is a bad FPR.