Help, i have a 1989 F250 with a 460 EFI. It is 2wd, heavy duty, duel tanks. I am having a fuel pressure problem. At idle i have almost 90 psi. the return lines are working and so are the supply. the engine is all over the place,running real rough. i can mix a can of paint on it. anyway, it is running very rich, the tailpipes are black. oh also all new plugs,wires,cap,rotor. and they are wired correctly. this problem was doing this before the tune up. any suggestions? thank you Daniel

 

Fuel Injection Technical Library » Fuel Pressure Regulator (FPR) Here is a link to testing the fuel pressure regulator (FPR), yours may be bad or the fuel return from it is blocked.
I would think you should have around 34psi fuel pressure at idle, with vacuum pipe connected and not kinked/leaking.

 

i disconnected the return lines and the have fuel coming back at a pretty good flow. i know the FPR has not been replaced. According to my repair manual it should have 35-45 psi at idle, I about had a heart attack when it read 90 psi and it was fluttering. as soon as I shut it off, it goes down to 35 psi and holds. i have a new FPR coming in the morning. I will let you know how it turns out. Thank you so much for the guidance. Daniel

 

Sounds like you may have a return line pinched or a bad (plugged) Fuel Selector valve.
Pull the vacuum line off the FPR and if you see no fuel coming out of the nipple on top when you turn the key on and off then I would dough that it is the FPR.

 

unfortunately the selector valve was bypassed. all the lines are flowing as they should.. checked for leaks and pinched or clogged lines, none. The TPS ohms out good and the IAC valve is good. I am trying the FPR tomorrow and see what happens. Thank you for the input, I will let you know how it turns out. Daniel

 

Ok, I looked at the fuel lines again before i did any other work. Turns out that I some how traced back the wrong line, they do cross over a few times.the plastic return line was kinked in several places, including on top of the rear tank, so I will have to drop the rear tank and replace the return fuel line. i believe I can use rubber fuel line instead of plastic. If I can that is what i will do. I'm so glad you guys were there for the advice and guidance, thank you very much, I hope to someday return the favor. if not, i love talking about ford trucks. Thanks again guys. Daniel

 

The return line is low pressure, it should not be an issue to replace it with rubber line.