A fuel tank assembly includes a shell defining an opening therein, an access panel connectable to the shell and movable between a closed position where the opening is closed and an open position where the opening is open, and a fuel tank disposed in the shell and slidably engaged with the shell. The fuel tank and the opening are dimensioned such that the fuel tank is slidable out of the shell via the opening when the access panel is in the open position. A generator assembly and a method of servicing a fuel tank of a generator are also described.