What was found
FLIGHT CREW REPORTED THAT DURING ENGINE START SMOKE ENTERED THE CABIN THROUGH THE AIR CONDITIONING DUCTS. THE FLIGHT CREW SHUT DOWN AND TURNED THE AIRPLANE OVER TO MAINTENANCE. MAINTENANCE INSPECTED ENGINE AND APU DRAINS AND INLETS. NO EVIDENCE OF OIL LEAKS WAS FOUND. ENGINES AND APU WERE RUN SEVERAL TIMES AND THE ACM WAS CYCLED BETWEEN HOT AND COLD USING ALL COMBINATIONS OF LEFT, RIGHT AND APU BLEED AIR. NO SMOKE OR OTHER DISCREPANCIES WERE NOTED. THE AIRPLANE WAS TEST FLOWN WITH NO SMOKE BEING PRODUCED. MAINTENANCE WAS UNABLE TO DUPLICATE THE DISCREPANCY.