Re: B-7800 dies suddenl while running, need help badly
Immediately after it dies and won't start, use a voltmeter to see if power is getting to the fuel shut-off solenoid. If not, you probably have a bad ignition switch.
Bear in mind I am not familiar with your tractor or its wiring, but that is what I would check. If you don't have a voltmeter, you could run a wire from the batter to the valve and see if it then starts up.