What was found
FUEL IMBALANCE WITH CENTER TANK PUMPS ON. RIGHT SIDE DROPS FASTER THEN LEFT SIDE. WITH CENTER TANK PUMPS OFF, LEFT AND RIGHT WING TANKS DROP AT SAME RATE. NO FUEL WAS TRAILING EITHER ENGINE. FUEL BURN WAS AS HIGH AS 2000 LBS LOW. SUSPECT POSSIBLE FUEL QUANTITY SENSOR PROBLEM. TOP OF DESCENT SHOWED 1500 LB BELOW PLANNED FUEL. GATE ARRIVAL SHOWED 700 LB BELOW PLANNED. ACCOMPLISHED FIM 28-21-00-810 FOUND UNWANTED FUEL. TRANSFER FROM CENTER TO LEFT TANK WITH CENTER BOOST PUMP OFF AND LEFT FORWARD BOOST PUMP ON, SUSPECT FUEL SCAVANGE FLOAT. AIRCRAFT WAS GROUNDED. REPLACED CENTER FUEL PUMP PER AMM 28-22-41. ACCOMPLISHED SATIFACTORY OPERATIONAL CHECKS IAW AMM 28-22-41-710-801. ACCOMPLISHED FUEL QUANTITY VERIFICATION IAW FUELING MANUAL 12-11-02.