What was found
SHORTLY AFTER LEVEL AT CRUISE SAW LEFT MAIN FUEL QUANTITY DECREASING WITH ALL 6 FUEL PUMPS ON WITH CENTER TANK FUEL, LEFT TANK SHOWED A 500 LBS DIFFERENCE FROM RIGHT MAIN TANK. RAN QRH FUEL LEAK CHECK LIST. DETERMINED NO LEAK WAS PRESENT. QUANTITY STOPPED DECREASING FROM LEFT TANK. AFTER CENTER TANK WAS USED GOT ABOUT A 700LB IMBALANCE FROM LEFT AND RIGHT TANK. BALANCED FUEL REST OF FLIGHT NORMAL. GROUNDED - YES. REFERENCE FIM 28-41 TASK 801. PERFORMED FUEL FQIS BITE CHECK. FOUND NO INFLIGHT FAULTS. FOUND NO CURRENT STATUS FAULTS. GROUND TEST PASS - NO FAULTS, REF AMM 28-22-00-730-802. PERFORMED CROSS FEED VALVE TEST - TEST PASSED NO FAULTS. REFERENCE AMM 28-41-00-720-801, PERFORMED FQIS COMPARISON CHECK - FOUND INDICATION WITHIN LIMITS.