A device is for a plastic gasoline tank for a motor vehicle. The device includes a frame, an internal reinforcing element of a gasoline system, and a movable support of the component. The movable support is attached to the frame and movable relative to the frame between an initial configuration in which the reinforcing element is at a first distance from the frame and a final configuration in which the reinforcing element is at a second distance from the frame. The first distance is smaller than the second distance. The frame is provided with a structure for stopping the movement of the movable support when the movable support is in the final configuration.