As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NUMBER 2 ENG START SWITCH DOES NOT STAY ENGAGED IN GRD AND NO ROTATION. GROUNDED - YES. B737-800 FIM 80-07 TASK 806, OPENED NR 2 ENGINE COWL. DISCONNECTED CANNON PLUG FROM START VALVE CB NOW STAYS IN AND START SWITCH STAYS IN GROUND POSITION. RECONNECT CANNON PLUG TO START VALVE AND WHEN START SWITCH PLACED TO GROUND START VALVE CB IMMEDIATELY POPS. REMOVED AND REPLACED NR 2 ENGINE START VALVE, LEAK AND OPS CK NORMAL. REF B737-800 AMM 80-11-03. GROUND VERIFICATION CHECK GOOD.