What was found
ATTEMPTING TO START USING A GPU, GPU WAS WORKING NORMAL AND HAD LIGHT OFF OF THE FUEL, ELECTRIC SYS WENT DEAD. THEN IT CAME BACK ON, CONTINUING TO TURN THE STARTER. QUICKLY TURNED OFF THE IGNITION SWITCH AND FUEL CUTOFF. NO HOT START, TEMPS GOT UP HIGH 300'S. ASSUMED THE FBO'S GPU DIED. HOOKED UP ANOTHER GPU. 2ND GPU STILL NOTHING, DID A NORMAL BATTERY START AND GOT TO OUR DESTINATION. ON OUR NEXT FLT, GPU HOOKED UP TO START, IT WOULD NOT POWER SHIP. JIGGLED GPU POWER CABLE AND PUSHED IT IN TO MAKE SURE IT HAD GOOD CONTACT AND POWER CAME UP. GPU WORKED FINE UP UNTIL THE STARTER MOTOR ON, AND NO POWER. A BROKEN GROUNDING STRAP THAT CONNECTS TO FIREWALL, BRACKET ATTACHED TO THE FIREWALL CRACKED AND ARCED ELECTRICITY FROM GPU, THROUGH STRAP. VIBRATION MAY HAVE CRACKED THE BRACKET.