What was found
FOLLOWING A FAILED START ATTEMPT OF THE APU IN FLIGHT AND A 2 MINUTE COOL DOWN AND A SUCCESSFUL START. THERE WAS A VERY STRONG ODOR OF FUEL IN THE COCKPIT AND CABIN. SHUT DOWN THE APU AND ODOR DISSIPATED. CW OPERATIONAL CHECK OF APU IAW AMM 49-10-00. OPS CHECK GOOD. BOTH PACKS ON APU AIR ONLY. NO UNUSUAL ODORS DETECTED. SUSPECT RESIDUAL FUEL FROM FAILED 1ST START ATTEMPT CLEARED AND NEXT APU START.