What was found
AFTER APU START AND APU BLEED AIR SELECTED WHITE SMOKE FILLED THE CABIN AND COCKPIT. "CORRECTIVE ACTION" ACCESSED AIRCRAFT. RECEIVED CUSTOMER SUPPLIED APU. REMOVED ALL APU ACCESS PANELS. REMOVED STARTER GENERATOR FROM APU. REMOVED ALL ACCESSORIES ATTACHED FROM AIRCRAFT. REMOVED APU FROM AIRCRAFT. REMOVED ACCESSORIES FROM REMOVED APU. INSTALLED ACCESSORIES ON REPAIRED APU. INSTALLED APU ON AIRCRAFT. INSTALLED ALL ACCESSORIES ATTACHED FROM AIRCRAFT. INSTALLED STARTER GENERATOR ON APU. INSTALLED BOTTOM APU ACCESS PANEL. PLACED SIDE APU ACCESS PANELS IN AFT BAGGAGE COMPARTMENT. SERVICED APU OIL. WORK PERFORMED IN REF TO CE680AS AMM 49-10-00. OPS AND LEAKS CHECKS REQUIRED. PUSHED AIRCRAFT OUTSIDE, PERFORMED MULTIPLE ENGINE RUNS AND LEAK CHECKS WHILE MOVING BLEED AIR TEMP FULL HOT TO COLD TO BURN OFF SMELL. NO LEAK NOTED. PERFORMED HOURS ECU INPUT. VERIFIED CORRECT INSTALLATION OF COMPONENTS. SERVICED ENGINE ONCE MORE AND CLOSED ALL APU PANELS, PERFORMED OPS CHECK OF APU GENERATOR AND APU. WORK DONE PER CE680A 80-10-25 AND 49-10-00.