What was found
(CAN) DURING REFUELING, FBO LINE CREW FAILED TO CARRY OUT SINGLE POINT REFUELING PRE-CHECK. DURING FUELLING, ONLY LT TANK WAS FILLED (RT REFUELING VALVE APPARENTLY FAILED IN THE CLOSED POSITION). BY THE TIME THE FLIGHT CREW NOTICED THE DIFFICULTY A SIGNIFICANT FUEL IMBALANCE HAD BEEN CREATED, REQUIRING CROSSFEED FROM LT TO RT TANK.