i just picked up a old 1988 super duty, had a hard time getting it started but when i did it seems to run real strong but it dies out and wont restart intermitently.... normally im a very good mechanic but im clueless with diesels.... at the fuel filter i measured under 3 psi@ idle other than that i dont know what to check..... also i was wondering what makes the engine turn off when you turn the ignition off on a diesel? is it just the fuel or is there a compresion relief also? im thinking this could be an electrical problem like an ignition switch or selenoied
Post here www.oilburners.net in the 6.9 and 7.3 IDI forum. I am Mr_Roboto there. If original your engine is a 7.3 IDI not to be confused with the 94+ 7.3 PowerStroke which is completely different. This is the same basic engine that is in my International rollback.
There is a fuel shutoff solenoid in the injection pump to shut off the motor. However your problem is likely not electrical in nature.
Normally if a diesel WILL start but dies then the problem is air in the fuel. There are two O-rings under each plastic tee at the injectors. These O-rings, when deteriorated, are a common point of air entry into the fuel system. These tees are part of the fuel return system and when the motor is shut off gravity pulls the fuel down and if there is any leak can pull air into the system. Normally but not always you will see a small fuel leak while running if there will be an air leak.
The mechanical injection system relies on pressure in the fuel injector lines to fire the injector. If air gets into the lines the air absorbs the injection pulse and the injector does not have the pressure to fire.
BTW Ford's light duty diesels are purchased from International / Navistar. With the exception of a few select parts, you can source engine parts at your International dealer at a substantial savings over a Ford dealer (who buys and reboxes International parts).
Conversely I am able to source engine parts for my International at big box auto parts stores by asking for parts for a Ford F-350, since they list pickup trucks but not MD trucks.
thank you jason and i think your right about the air im starting to slowly understand how these things work i will probably just change all those o rings and fuel lines and go from there, i will post up the results
i took the easy way out and let a diesel shop take care of it, what they found was a defective switch over valve and fuel lines from the tank to the lift pump so they bipassed the switch over valve and ran a new fuel line from one tank to the lift pump making the other tank usless......its running great now 368 bux but well worth it