What was found
2HRS INTO FLIGHT AT FL410, FWD AND AFT LEFT FUEL PUMPS BEGAN FLICKERING LOW PRESSURE VIA PRESS LIGHTS. OPENED THE CROSS FEED VALVES, LIGHTS EXTINGUISHED. A FUEL IMBALANCE QUICKLY BEGAN TO DEVELOP, MAX 1,300LBS. DESCENDED TO FL250 TO SUCTION FEED THE LEFT MOTOR. AT 25,000 - CLOSED THE CROSS FEED VALVES AND THE LOW PRESSURE LIGHTS BEGAN FLICKERING AGAIN WITH OCCASIONAL ICAS MSG L AFT/FWD FUEL PUMP. QRH REFERENCED. FUEL FLOW WAS STABLE. SITUATION REMAINED TO AN UNEVENTFUL LANDING EMERGENCY DECLARED. ***EMERGENCY DECLARED*** TROUBLESHOT PER FIM 28-22 FIG 806. DID NOT FIND ANY CIRCUIT BREAKERS POPPED. FUEL BOOST PUMPS OPERATED CORRECTLY. TRANSFERED FUEL FROM L/H TANK TO R/H TANK AND FUEL MOVED AS REQUIRED. REMOVED AND INSTALLED RELAYS K188 AND K187 PER 757 AMM 28-22-15-4 UP TO AND INCLUDING STEP E. (5) A. STILL REQUIRES OPS CHECKS AMM: 28-22-00-5, 28-41-00-5-1 757 COMPLETED L TK PUMPS & GFI TESTS. ALL TESTS OK. AS PERCAUTION PERFORMED DRY CAPACITANCE CK OF L TK COMP & POBES. ALL READINGS WITHIN NORMAL LIMITS. XFRD FUEL FROM & TO L TK. ALL QTY'S AGREE.