What was found
DURING START, NR 1 ENGINE DID NOT EXCEED 30 PERCENT, PILOT ABORTED THE START AND USED BATTERY CART TO START THE AIRCRAFT. NO POWER FROM BATTERY CART, APU CIRCUIT BREAKER POPPED, UPON RESET THE PILOT OBSERVED A SPARK FROM THE OVERHEAD CIRCUIT BREAKER PANEL. THE MECHANIC REMOVED AND REPLACED THE FUEL CONTROL, AIRCRAFT BATTERY AND REPAIRED THE AIRCRAFT APU WIRING. THE AIRCRAFT WAS RETURNED TO SERVICE.