What was found
APU FAILED TO START. FAULT LIGHT ILLUMINATED & EICAS MSG. APU FAULT DISPLAYED. ADDITIONAL START ATTEMPTS UNSUCCESSFUL. REPLACED APU STARTER & APU CRANK CONTACTOR. FOUND A 2" DIAMETER HOLE IN STARTER MOTOR CASING. REPLACED APU STARTER, AUTO SHUTDOWN WITH "LOP" FAULT. APU AUTO SHUTDOWN AT 90 PERCENT RPM. ECU FAULT DISPLAY "LOP", FAULT UNIT "STARTER CIRCUIT". STARTED T-S REF FIM 49-11-00 FIG 109. REPLACED LOP, NO HELP. REPLACED OIL FILTERS IAW FIM. START OK. HEAVY SMOKE FROM STARTER AT SHUTDOWN. SUSPECT STARTER NO CUTOUT. REPLACED STARTER & CRANK CONTACTOR, NO HELP. TRIED NEW ECU & START RELAY K197, NO HELP. 1ST START ATTEMPT OK. 2ND ATTEMPT BURNED OUT STARTER. REPLACED STARTER AGAIN. OPS NORMAL.