What was found
PILOTS NOTICED 400 LBS DROP IN FUEL QTY WITHIN 15 MINUTES OF FUELING, APU OFF. ACFT GROUNDED. PERFORMED FUEL QTY OPS TEST IAW AMM 28-41-00-801, NO FAULTS FOUND. FQIS SYS PERFORMED FUEL STICK COMPARISON WITH FLIGHT DECK SYS, FOUND DIFFERENCE TO BE 180 LBS DIFFERENCE RT WING POSITIVE IN TANK, COMPARISON TEST IAW 28-41-00. OPS CHECK OK FOR SERVICE. FAULT HISTORY LOGGED 20 COUNTS OF NR 1 MAIN TANK COMP DATA BAD AND NR 2 MAIN 21 COUNTS OF COMP DATA BAD. DEFUELED NR 1 AND NR 2 MAIN TANKS. OPENED TANKS AND REMOVED ICE AND WATER ACCUMULATION UNDER COMP PROBES FOR NR 1 AND NR 2 MAIN TANKS. REPLACED NR 1 MAIN TANK COMPENSATOR, REF AMM 28-41-21/401. REPLACED NR 2 MAIN TANK COMPENSATOR, REF MM 28-41-21. FUEL TANKS CLOSED WITH OK TO CLOSE ON T/C 78528000. ACCOMPLISHED FQIS BITE TEST. NO FAULTS NOTED, REF FIM 28-41/801.