What was found
OIL QTY INDICATION (ENGINE) SHOWS LOW QTY, DEPLETED TO ZERO 9.5 HRS INTO FLT WITH DROP IN PRESSURE. 18 QUARTS OF OIL WERE ADDED TO THE TANK. NOTHING OBVIOUS FOUND DURING THE UNDER COWL VISUAL INSPECTION WITH THE ENGINE NOT RUNNING. RAN LT ENGINE AT POWER ASSURANCE NUMBERS FOR. 5 MINS, PART POWER FOR 10 MINS. FOUND OIL COMING OUT DRAIN MAST LABELED TBV MFP. REMOVED NR 1 ENGINE MAIN FUEL PUMP IAW AMM 73-11-01-00A-520A-A. REMOVED AND REPLACED ACCESORY GEARBOX MAIN FUEL PUMP CARBON SEAL IAW AMM 72-64-01-00A-720A-A. INSTALLED NR 1 ENG MAIN FUEL PUMP IAW AMM 73-11-01-00A-720A-A. PERFORMED IDT INSPECTION OF NR 1 ENGINE MAIN FUEL PUMP IAW AMM 73-11-01, AND GMM 09-10-05. ORIGINAL FUEL PUMP REINSTALLED AFTER GEARBOX CARBON SEAL REPLACEMENT. VERIFIED ALL SEAL, TORQUES, SAFETY,SECURITY AND LEAK CHECKS. LEAK CHECK GOOD.