What was found
FMC FUEL DISAGREE MESSAGE ON PROG PG 2 WITH ASSOCIATED DECREASE IN LEFT MAIN TANK QUANTITY. VISUAL CONFIRMATION OF FLUID/VAPOR FROM LEFT WING/ENGINE AREA. COMPLIED WITH QRH PROCEDURE 120.3 FOR FUEL LEAKAGE. SCREEN CONFIRM SOURCE OF FUEL LEAKAGE. ACCOMPLISHED GROUND ENGINE RUN WITH NO LEAKS OR DEFECTS NOTED. FUEL IMBALANCE NULLIFIED BY USE OF THE APU. REPLACED SEALS AND HARDWARE ON BOTH ENDS OF FUEL SUPPLY 73-11-06-06 ITEM 250 AND 72-00-00. AND CROSSFEED IAW AMM 73-11-06.