What was found
TANK 2 PUMPS OFF ILLUMINATED ON DURING CRUISE FLIGHT. MONITORED FUEL DISPLAY. FUEL BEING FED TO NR 2 ENGINE VIA CROSSFEED FROM EITHER NR 3 OR NR 1 TANKS, ALTERNATING AS NECESSARY TO MAINTAIN BALANCE. FUEL TANK 2 QTY DROPPED TO 6200 LBS THEN CAME UP TO 7200 LBS WITH NO FUEL BEING TRANSFERRED INTO TANK 2. FLUXUATION CONTINUED AND INCREASED UNTIL ALERT LEVEL 2 "FUEL QTY FAULT" ON. ON FLT CREW DEBRIEF, WAS TOLD FUEL QTY WENT UP AND DOWN THOUSANDS OF LBS UNTIL IT FINALLY WENT TO X ON SYNOPTIC. TRIED PERFORMING RTS ON FSC SEVERAL TIMES, EACH TIME FAILED TANK NR 1, NR 3 TANK OTBD FILL VALVES. ORDERING FSC AND AUX CONTROLLER. R & R FSC AND ANCILLARY FUEL CONTROLLER IAW MM 28-08-01-4 AND 28-08-03-4. PERFORMED RTS IAW MM 28-00-00-5, SAME CONDITION EXIST , FAILS BOTH NR 1AND NR 3 OTBD FUEL VALVE. REPLACED THE NR 2 TANK LT COMPENSATOR PROBE REF A/C M/M 28-41-01-2 WILL NEED LEAK CHECK.