What was found
FA REPORT FUMES AROUND MID/AFT CABIN. FUMES LASTED A FEW MINUTES AND HAPPENED EXACTLY AT ENGINE START NR 1 ENGINE WAS STARTED WITH APU ON - BLEED ON. C/W MSI STEP STEP A. FLIGHT CREW REPORTED FUEL ODOR WENT AWAY AFTER A FEW MINUTES. C/W STEP (B). MCC CONCURED. C/W STEP (C). C/W STEP (D). REPORT TURNED IN. C/W STEP (E). W/C #0550-2002 STEPS 1 -4 C/W. W/C #0550-2002 C/W. DETERMINED W/ CREW CAUSE WAS AMBIENT AIR AT LOC. NO TROUBLE FOUND A/C OK FOR SVC. (LP: 8273990). AIRCRAFT WAS GROUNDED