I have a 87 F250 with a zf5 transmission and a 6.9 idi. I was having trouble with it stalling out and a rough idle did some research when I figured out I had a fuel leak i looked and it was from a bad o ring on my injectior so I get a kit and change the o rings, injectior caps, the fuel line, and the fuel filter then i bleed the fuel lines and she started up . But it still wouldn't go in overdrive without losing function in my accelerator pedal and stalling and having a rough idle sometimes . So then I changed my lift pump and she started right up but nothing happened when I tried to bleed the fuel lines but I tested it out I could go into overdrive and everything still rough idle but no stalling for a week and a half until today it's stalled 4 times and wasn't tryna start back up and idk what to do next on it the next thing back on the lines is the fuel tank from what I can see.

 

How many miles? Injector pump may be worn out.

 

You said ZF5 transmission which is a manual transmission correct? I am not aware of any lock out that would prevent shifting into that gear. Could you explain a little more?

What sort of test equipment do you have or can borrow?

 

It could be your IP, try running the fuel and return from a Jerry can, with a fuel pressure gauge also installed.

With verifiable running positive fuel pressure, from a small fuel jug, it will run just fine if there is no problem with the IP.

You should eliminate failure points and have a gauge for fuel pressure, 2-7 psi is fine 5-6 psi is ideal, you cant know that the lift pump is okay without a gauge, alot of new ones are junk out the box.

If it's already running, injector I ring leaks won't cause rough running or idle, they'll just leak out all your diesel,

one donought gasket I ring on top, that could cause that problem would be the one connecting the hardline from the fuel filter to the center inlet fitting on the back of the IP main inlet.

That one can easily leak, and cause running issues, if your lift pump is weak esp, below 2 lb draw as the suction 2 lb draw of the pump could suck air if the lift pump is inadequate.

First get a fuel psi gauge installed, second plumb your fuel direct from a jug, eliminate and find your failure point, if it is all tight and you have psi, and there is no potential for failure points left, then it's your IP,.

I always add a little new clean motor oil or 2 stroke oil or oil to my fuel, for lubricity or you will wipe your IP internals out, these are designed for fuel oil, not ulsd, pump will last 2x and they're espendy.