What was found
DURING TAKEOFF WITH ENGS & APU RUNNING, ODOR OF FUEL & EXHAUST IN COCKPIT. SMELL DISSIPATED ABOUT 2000 FEET AGL. SHUTDOWN APU, ODOR DID NOT REOCCUR DURING FLIGHT. RAN APU, LT & RT ENGS TO TAKEOFF POWER. COULD NOT DUPLICATE DISCREPANCY. INSPECTED ENGS FOR FUEL LEAKS, NO LEAKS FOUND. INSPECTED APU, FOUND FUEL NOZZLE AT THE 5 O'CLOCK POSITION B NUT & CONNECTING FUEL LINE B NUT LOOSE. TIGHTENED B NUTS & RAN APU FOR LEAK CHECK. LEAK CHECKS GOOD IAW MM 49-30-06. LEAK & OPERATIONS CHECKED GOOD, CLOSED ACCESS ITEMS. COMPLIED WITH TASK CARD TC-680-21-120905M ECS DUCT BURN OUT.