AN ACR FLC FINDS THAT THE ACFT HAD BEEN MISFUELED DURING THE LAYOVER. HOWEVER; DURING THEIR ATTEMPT TO TRANSFER THE FUEL THEY CONCLUDE THAT THE GAUGE WAS INCORRECT AND GO. INFLT THEY DISCOVER THAT THE ACFT REALLY HAD BEEN MISFUELED.

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WE BROUGHT ACFT IN THE NIGHT BEFORE. ON RETURNING TO ACFT THE NEXT MORNING WE DISCOVERED THAT IT APPEARED TO BE MISFUELED (LIMITATIONS OF ACFT STATED THAT YOU CAN'T HAVE MORE THAN 1000 LBS OF FUEL IN CTR TANK UNLESS THE MAIN TANKS ARE FULL). WE HAD SHOWING 5300 LBS IN #1; 6000 LBS IN #2; AND 3800 LBS IN THE CTR TANK. WE TALKED TO THE LCL OPS PEOPLE AND THEY SAID THAT THEY DID NOT CALL FOR FUEL TO BE ADDED TO THE CTR TANK. WE THEN ATTEMPTED TO TRANSFER FUEL FROM CTR TANK INTO MAINS; BUT THE CTR TANK BOOST PUMPS WOULD NOT PRESSURIZE. SO NOW WE BELIEVED THAT THE CTR TANK GAUGE IS INOP (IN ERROR) BECAUSE NO FUEL IS BEING PICKED UP. SO BEING AN A&P MECH I DECIDED TO SWAP FUEL GAUGES. I ALSO CHKED THE CIRCUIT BREAKERS; NO HELP. IN SWITCHING GAUGES I DISCOVERED THAT THEY COULD NOT BE SWAPPED BECAUSE THEY HAD DIFFERENT PART NUMBERS SO I INSTALLED THEM BACK IN ORIGINAL PLACES AND RESET THE CIRCUIT BREAKERS. WE THEN CHKED THE MEL WHICH SAID WE COULD GO WITH CTR TANK GAUGE INOP PROVIDING WE USED ANOTHER METHOD TO VERIFY FUEL QUANTITY. WE THEN AGREED THAT IF WE ADDED 500 LBS TO THE CTR TANK AND THE LOW PRESSURE LIGHTS WENT OUT THAT IT WOULD VERIFY THE TANK WAS EMPTY AND THAT AFTER FUELING WE HAD 500 LBS. SO AFTER THEY ADDED THE 500 LBS THE LOW PRESSURE LIGHTS WENT OUT. SO WE SHOWED THIS CORRECTION ON OUR WT AND BAL RECORD AND DEPARTED NORMALLY. ENRTE WE TURNED ON CTR TANK BOOST PUMPS TO BURN OUT THE 500 LBS. NOT ONLY DID IT BURN 500 LBS; BUT IT CONTINUED TO BURN FUEL OUT OF CTR TANK TILL WE ARRIVED AT THE GATE IN SLC. SO NOW THIS SHOWED US THAT THE GAUGE WAS NOT IN ERROR AND WE ACTUALLY HAD 3800+ LBS FUEL IN THE CTR TANK. HAVING THIS 3800+ LBS; THE 500 LBS WE ADDED GAVE US AN INCORRECT WT AND BAL SHEET.