What was found
PDIS 303 28-40 7724 21AUG21 IND OPEN U APPROXIMATELY 30 MIN INTO CRUISE TNK 1 FUEL QTY LO, TNK 1 TIP TRAPPED ALERTS ILLUMINATED. APPROXIMATELY 7700 LBS OF FUEL ACROSS EACH TANK.. TANK 1 STOPPED FEEDING AT 7500. SELECTED MANUAL, THEN AUTO, NO HELP. IN STEEP DESCENT WITH SPOILERS FULLY DEPLOYED. ALERTS EXTINGUISHED AND FUEL CONTINUED ON SCHEDULE. EMERGENCY DECLARED. SHGN 21AUG21 02:23 IND U PERFORMED FUEL QUANTITY TEST, TEST PASSED NO FAULT NOTE REF AMM 28-41-00-5-0. ALSO PERFORMED FSC TEST REF AMM 28-08-01-5 NO FAULT NOTED. MCDU SHOWN NO FAULT HISTORY, NEED MORE TRUBLESHOOTING. RNR O RING ON FUEL PUMP PRESSURE LINE FROM INBD FLOAT VALVE TO OUTBRD TRANSFER VALVE IN #1 MAIN TANK REF MD10AMM 28-00-01-2 OPS CHECK GOOD NO FUEL TRAPPED IN #1 TIP TANK. WORK PERFORMED BY STS TANK TIGERS INC WO#12144R668