I have a 2003 B7800. Fuel solenoid not receiving 12 volt to start. Sometimes will sometimes won't. Wiggle fuse block or let sit a while and it will start. I hear a loud click when right. 30 amp fuse is receiving voltage
It appears you've got a loose or dirty connection somewhere. You seem to have a handle on your problem, though. It's good your thirty amp fuse is receiving voltage. Is the fuse itself possibly intermittent and not passing the voltage? Or maybe the connection is loose or slightly corroded? Try tracking back from the fuel solenoid when it's not getting voltage to see where the voltage stops.