PILOT REPORTS A B737-800 HAD TWO PREVIOUS WRITE UPS OF FUEL TRANSFERRING PAST THE CROSSFEED VALVE INFLIGHT LEADING TO AN IMBALANCED CONDITION BETWEEN MAIN (WING) TANKS.

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ACFT HAD 2 PREVIOUS WRITE-UPS OF FUEL XFERRING PAST THE XFEED VALVE INFLT LEADING TO AN IMBALANCED CONDITION BTWN MAIN (WING) TANKS. CLOSEST MAINT DEFERRED ITEMS CODE USED TO DESCRIBE PROB WAS FOR SLOW OR STICKING XFEED VALVE ALTHOUGH ALL WRITE-UPS OF PROB WERE VERY SPECIFIC THAT IT WAS A XFLOW PROB WITH THE VALVE INDICATING CLOSED; NOT A VALVE SPD PROB. I REPEATED THE WRITE-UP AS THE PROB STILL EXISTED AND REQUESTED MAINT MEET THE ACFT ON ARR SO AS TO EXPLAIN THE PROB IN EXACTING DETAIL FACE-TO-FACE. MAINT MET THE ACFT AND RELATED THAT HE HAD ALREADY BEEN IN CONTACT WITH MAINT CTL AND THAT THEY RECOGNIZED THE TRUE CULPRIT WAS THE XFEED VALVE. IN THAT 'THEY' DID NOT HAVE A VALVE TO CHANGE OUT; 'THEY' WERE GOING TO CHANGE THE 2 TANK BOOST PUMPS ON THE HVY SIDE SO AS TO BALANCE THE PRESSURES BTWN THE TANKS; THUS MITIGATING THE XFER UNTIL THE XFEED VALVE COULD BE CHANGED AT SOME TIME IN THE UNCERTAIN FUTURE. THE ACFT HAD A KNOWN HISTORY WITH SEVERAL ATTEMPTS TO FIX IT USING THE SAME PROC CHKING FOR BLOW-BY ON THE GND. YET THE PROB REPEATED IN THE AIR; IN ACTUAL USE CONDITIONS. CHKING THE ACFT MAINT HISTORY THIS MORNING; I NOTICED A CONTINUATION OF THE GND CHK FOR BLOW-BY THAT DIDN'T WORK BEFORE AND NOW AN APPARENT DEFERRAL OF THE ITEM NUMBER ACFT MAINT HISTORY RECORD OF A DOUBLE PUMP CHANGE. SO THERE IT IS FOLKS. NO PART AVAILABLE. PROB KNOWN TO A CERTAINTY. MAINT PROC IMPLEMENTED TO THE WRONG PART OF THE SYS SO AS TO ANSWER THE SQUAWK AND KEEP THE ACFT MOVING UNTIL IT BECAME CONVENIENT TO ACTUALLY FIX IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED EVEN WITH MATCHED FUEL CONSUMPTION; ONE WING TANK WAS SHOWING NOTICEABLE FUEL IMBALANCES; EVEN THOUGH THE CROSSFEED VALVE ON THE B737-800 WAS INDICATING CLOSED.