MLG HAS FUEL INCONSISTENCY. LANDED WITH 1000 POUNDS; NOT REFUELED BUT SHOWS 17000 POUNDS. AFTER TKOF; DISCOVER THEY DO NOT HAVE ENOUGH FOR TRIP.

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WHILE CONDUCTING THE 'BEFORE START' CHKLIST FOR ACR FLT I NOTICED THAT THE FUEL QUANTITY INDICATORS REFLECTED 17000 POUNDS OF FUEL. THE ACFT PMS COMPUTER INDICATED THAT WE HAD 10100 POUNDS OF FUEL WHICH WAS THE QUANTITY WE HAD UPON ARR AT LGA. THE PMS ALSO INDICATED A FAULT WITH THE FUEL QUANTITY UPDATE. WHEN MAINT WAS CONSULTED; THEY INDICATED THAT THE ACFT SHOWED 17000 POUNDS OF FUEL ON BOARD. WHEN THE FUEL TRUCK DRIVER RETURNED; HE CLAIMED THE ACFT HAD NOT BEEN FUELED BUT HAD 17000 POUNDS ON BOARD. WE DISPATCHED WITH THE ASSUMPTION WE HAD IN EXCESS OF THE 14700 POUNDS REQUIRED FOR THE TRIP. UPON ROTATION; IT WAS OBVIOUS THAT A SIGNIFICANT FUEL IMBALANCE EXISTED. WE ALSO NOTICED THAT THE FUEL QUANTITY HAD NOT DECREASED SINCE WE HAD LEFT THE GATE. THE FO FOUND THE FUEL QUANTITY CIRCUIT BREAKER POPPED WHICH HE RESET. THE INDICATED FUEL QUANTITY STARTED TO DROP AND THE FUEL IMBAL WAS CONFIRMED. WITH LESS FUEL ON BOARD THAN REQUIRED FOR DISPATCH; WE ELECTED TO RETURN TO LGA WITH A ROUTINE LNDG.