Had a problem last winter, 93 F250 diesel that would start immediately, run for 5 seconds, then quit. Would have to crank and crank and it would finally start and run fine. Mechanic said the pump was bad and replaced it and guess what, it did the exact same thing. Lots of fiddling, and denying that pump wasn't the problem got it to start and run but does so poorly. Anyone experience this type of problem?

rboett3930@a0l.com

 

Leaky return lines and o-rings on the injectors.

 

I must agree with Malcolm. Either the return fittings are leaking or the lift pump is bad

 

Yes, leaky return lines, o-rings and mechanical pump on the side of the block. My brothers '86 did exactly what you describe. We replaced o-rings and hoses. It still did it. Then we replaced the "new" fuel pump. It was on there when he bought it. Problem solved. I think he drove it about a year like that before we fixed it. He would start it and rev it up high to keep it running for about 10-15 seconds then it was fine. That trucks long gone with over 300.000 when he upgraded to a '97.

 

I have a '90 F250 7.3L
I am have very similar problems. It will start after much cranking and bleeding off of air in the system. Run for 1200 yards then die and the cycle begins all over again.
I have vaccum and presure tested the fuel lines. It does it on either tank. I have replaced the lift pump and the tank transfer switch. I have placed a clear plastic line on the fuel return line to the NEW fuel filter to view the air in the system. This line never does fill up all the way when it is running.
It begins black smoke,increased RPM, Rough running and then dies in that order.
Could this problem be the same in that the Injector O Rings are bad ???
I have no fuel leaks at any point but I am sure the air is getting in some how.
None of the parts replaced so far have changed the symptoms at all.
If anyone has a suggestion feel free to E-mail it to me directly. I am getting desparate enough to have it towed to a factory ford repair shop and pay dearly for the service.

 

TekJim,
I was at a fuel rebuild shop last week getting some tractor injectors tested. In the conversation with them about 6.9 run/not run problems they said start/run and die problems are almost always air intruding into system. Hard starting initially is usually lack of fuel related.

I know that is general information, but for $30 you can replace all the return line hose, clamps, "t"'s and "o" rings. That gets a big part of air infiltration locations!

 

Thanks for the input, took it to Ford and they sent in the injectors for testing, said they were all poor, and replaced them. Ran slightly better, doesn't die after starting but takes more cranking than I like (10 to 15 sec) and doesn't run that well for about 2 min. or so. However I still have diminished power and with a 5,000 pound trailer I can barely make 70 without pushing the floorboards out. Someone here mentioned problems with replacement exhausts being too restrictive and did have them replaced last year, might check that.
How do you test the return lines for air seal?