A fuel cap operable to close an opening of a fuel tank. The fuel cap includes an outer shell having a protrusion and a shell locking member. The fuel cap includes a detection mechanism for sensing a level of fuel within the tank. The fuel cap further includes an assembly component engageable with the outer shell to support the detection mechanism on the outer shell. The assembly component defines a groove operable to receive the protrusion. Additionally, the assembly component includes a component locking member. The outer shell and the assembly component are engageable with one another by a relative axial movement followed by a relative rotational movement about an axis. Once engaged, the outer shell and the assembly component are fixed against disengagement by engagement of the shell locking member and the component locking member.