What was found
AFTER ENGINE START GOT EICAS MSG: L PACK OFF. AFTER ADVANCING THROTTLE TO TAXI, MSG EXTINGUISHED. TAKEOFF POWER WAS COMPUTED FOR DTO 50 WITH TEMPERATURE MINUS 6 CELSIUS. ON RUNWAY AFTER THRUST LEVERS WERE ADVANCED TO TAKEOFF POWER AT APPROXIMATELY 100 KNOTS, EICAS MSG: L ENG BLEED OFF ANNUNCIATED. DURING THE CLIMB TO A SAFE ALTITUDE HE EICAS MSG: L ENG BLEED OFF EICAS EXTINGUISHED AND ILLUMINATED A FEW TIMES. AFTER SAFE ALTITUDE WAS REACHED COMPLIED WITH QRH ENGINE BLEED OFF PROCEDURE. AFTER NOTIFYING GOC, THEY DIRECTED A DIVERT TO MEMPHIS. REMOVED LEFT REVERSE FLOW CHECK CONTROLLER IN REF TO 757 AMM 36-11-18-4. NEW PART AND HARDWARE IS IN 114 LINE SHACK. INSTALLED L/H ENGINE REVERSE FLOW CHECK CONTROLLER REF. 757 AMM 36-11-18-4. OPS CHECKED GOOD.