M809 / M939 series No power/No start - Bad PCB Box - Bypass to Start / Rebuild 

This is a video on how to bypass your Power Control Box (PCB) on a M809, M939 with a NHC250 or 8.3L Cummins to get the truck to start in a pinch. You really do not need the big electrical wire at all to jump terminals. That will however send power to the fuel shut off solenoids. Otherwise you just simply need to jump the starter if you combat mode or your fuel shut off solenoid on the A2 truck is removed.
This also shows you how to rebuild them fairly easy- Cole Harsee 24063 solenoid.