What was found
DURING CLIMBOUT, THE LEFT FUEL TANK NR 1 PUMP LOW PRESSURE LIGHT ILLUMINATED FOR APPROXIMATELY TWO MINUTES THEN RETURNED TO NORMAL. DUE TO NR 2 PUMP CURRENTLY ON MEL, AIRCRAFT RETURNED TO LAS AND LANDED WITHOUT INCIDENT. MAINTENANCE DRAINED WATER FROM THE LEFT AND RIGHT FUEL TANKS, REMOVED THE NR 1 PUMP LOW PRESSURE SWITCH AND PURGED THE FUEL LINE, OPERATIONAL CHECK OK.