FUEL TRANSFER TO CENTER TANK RESULTING IN LOW FUEL WARNING WHEN MAINS WERE DOWN TO 2000 POUNDS.

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DEPARTED LGW FOR BWI WITH 100000 POUNDS FUEL. FLT WAS NORMAL AND FLT PLAN WAS KEPT ACCURATELY ON OVER OCEAN PORTION. LAST CHKPOINT WAS TUSKY. APCHING BOS EICAS LOW FUEL WARNINGS OCCURRED. A RAPID CHK OF THE FUEL SYS SHOWED 2200 POUNDS L MAIN 2700 POUNDS R MAIN AND 22300 POUNDS CENTER TANK. IMMEDIATELY TURNED ON CENTER PUMPS AND COMPLETED LOW FUEL CHKLIST. THIS WAS THE FIRST TIME WE HAD A 'FUEL CONFIGN' WARNING AND LIGHT. FUEL CONFIGN WARNINGS FOR LOW FUEL ARE ALSO SUPPOSED TO OCCUR ANY TIME THERE IS MORE THAN 1200 POUNDS IN THE CENTER TANK AND CENTER TANK PUMPS ARE NOT ON. THIS WARNING NEVER OCCURRED. I HAD JUST READ ABOUT A MFR'S PROBLEM OF LEAKY CHK VALVES ALLOWING FUEL TO BE PUMPED FROM THE MAINS THROUGH A CHK VALVE IN THE CENTER TANK PUMP TO REFILL THE CENTER TANK. NORMALLY THE FUEL CONFIGN WARNING WOULD ALERT YOU. IN THIS CASE IT DID NOT. WE REALIZED THAT THE TRANSFER MUST HAVE HAPPENED SOMETIME AFTER 'TUSKY'. DUE TO WX IN BWI AND THE FACT WE KNEW THERE WAS A PROBLEM IN A CENTER TANK PUMP WE DIVERTED TO NEAREST SUITABLE ARPT; JFK. LATER ON THE GND I DID SOME BOOK WORK AND DISCOVERED THAT HAD WE NOT HAD LOW FUEL WARNINGS OR HAD BELIEVED IT TO BE AN INDICATION PROBLEM AND NOT TURNED ON CENTER PUMPS; BOTH ENGS WOULD HAVE FLAMED OUT. NO AC PWR WOULD HAVE BEEN AVAILABLE. NO APU BECAUSE IT'S FUEL SOURCE IS THE MAIN TANKS. NO WAY TO GET AT THE FUEL IN THE CENTER TANKS BECAUSE THE PUMPS ARE AC PWR. NO FLAPS; ENGS OR COMPUTERS JUST THE BATTERY AND 185 PEOPLE WAITING FOR US TO DEADSTICK A WDB WITHOUT PWR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. FAILURE OF THE FUEL CONFIGN LIGHT WAS CAUSED BY COMPUTER CHIP PLUG PIN BENT; SUSPECT IT HAPPENED DURING MANUFACTURE. ACFT WAS DELIVERED IN 1982. FUEL GAUGES ARE ON THE OVERHEAD PANEL; LIQUID CRYSTAL INDICATORS; VERY SMALL AND DIFFICULT TO READ. AT THE WAYPOINTS A RECORD IS KEPT OF THE FUEL REMAINING BUT TOTAL FUEL IS GENERALLY THE ONLY GAUGE READ; NO MORE AFTER THIS INCIDENT. THE FLT HAD BEEN CLRED DIRECT BOS AND THE LAST WAYPOINT WAS BYPASSED RESULTING IN NO FUEL CHK BEING MADE OR ENTERED ON THE FLT PLAN; A PERIOD OF ABOUT 2 HRS. THIRD CREW MEMBER HAD A COPY OF BULLETIN REF THE FUEL TRANSFER PROBLEM FROM THE MAINS TO THE CENTER TANK. DIVERTED TO JFK ACCOUNT WX IN BWI AND THE UNCERTAINTY OF THE FUEL SYS IN GENERAL. CREW WAS GIVEN A CHK RIDE OVER THE SAME RTE. FEELS THE EICAS MESSAGE SAVED THE DAY.