I have 91 L 8000 and am looking for a schematic on the start/run circuit for the Bosche fuel injection pump control solenoid. The solenoid pulls in with the key in the start position, as soon as the key is released to the run position, it looses power and releases, turning off the fuel flow.

 

Probably not what you want to hear, but did you check all the fuses?

I've noticed a lot of "start" and "run" circuits are sometimes powered by two different fuses on all sorts of vehicles.

 

I have checked all the breakers, fuses and relays. I am going to test the run side of the ignition switch next. Thanks for the suggestion.