THE PREVIOUS POST PRETTY MUCH COVERS ALL TH POSSIBLE PROBLEMS FOR YOUR SYMPTOMS. THE PRIME BUTTON IS ACTUALLY A PRE-HEAT (GLOW PLUG) SWITCH THAT ALSO RUNS THE ELECTRIC FUEL PUMP TO PRIME THE FUEL SYSTEM. THIS SWITCH WHEN ENERGIZED BYPASSES THE CONTROL BOARD AND APPLYS POWER DIRECTLY TO FUEL PUMP AND RUN SOLENOID. WHEN CRANKING, AS GENERATOR COMES UP TO SPEED AND A.C. VOLTAGE IS PRODUCED, THE CONTROL BOARD TAKES OVER, AND SUPPLIES POWER TO FUEL PUMP AND RUN SOLENOID. THEN YOU RELEASE START SWITCH, AND IT CONTINUES TO RUN, iF THE GEN SHUTS OFF WHEN YOU RELEASE THE SWITCH, THEN YOU LIKELY HAVE A BAD CONTROL BOARD, OR NO A.C. POWER BEING PRODUCED FROM GENERATOR. lIKELY CAUSES OF NO A.C. POWER ARE FIELD BRUSH WORN OUT OR STUCK, NOT CONTACTING ROTOR SLIP RINGS, BAD VOLTAGE REGULATOR, OR (WORST CASE)OPEN OR SHORTED WINDINGS IN GEN ROTOR OR STATOR. YOU CAN"T JUST JUMPER THE GLOW/PLUG/PRIME SWITCH, FOR VERY LONG, OR YOU WILL OVERHEAT GLOW PLUGS AND DESTROY THEM.
THIS IS A VERY DIFFICULT SYSTEM TO DIAGNOSE, AND AS O.P. SAID PARTS ARE GETTING TO BE SOMEWHAT OF A CHALLENGE. IF GEN END HAS GONE BAD (ROTOR OR STATOR) SET IS PROBABLY NOT COST EFFECTIVE TO REPAIR, THE CONTROL BOARDS ARE AVAILABLE, SEVERAL HUNDRED $$, AND MAY BE ALL YOU NEED.
