What was found
RETURN TO GATE. FOR NR 2 HUNG START AND STRONG FUEL ODOR DURING START. RT ENG DID START NORMALLY USING AUTO START. RTBL, FUEL ODOR IN FLT DECK & VERY STRONG ODOR IN AFT CABIN AS REPORTED BY F/A. MAINT CHECKED BOTH ENGINES AND APU FOR LEAKS, NONE FOUND. RAN APU AND BOTH ENGINES WITH PACKS BOTH PACKS, ONE PACK AT A TIME USING ENG AND APU BLEED AIR , MAINT CHECKED CABIN AND FLT DECK FOR EVIDENCE OF FUEL ODOR, NONE REPORTED,