A locking cap for a threaded filler neck includes a closure member for engaging and closing the neck, a shell providing a hand grip and including a key-actuable lock, and a race disposed for rotation between the shell and closure. The race includes axially inwardly opening pockets, and the closure includes flexible pawl fingers for engaging the pockets to provide a driving connection between the closure and race which is positive in the cap-removal direction and torque-limited in the cap-advancing direction. The race also includes a set of peripherally spaced, radially inwardly projecting teeth, and the shell is molded to provide a pair of flexible drive fingers for engaging the peripherally spaced and radially inwardly projecting teeth to provide a driving connection between the shell and race which is positive in the cap-advancing direction and torque-limited in the cap-removal direction for free ratcheting of the cap when it is in position on the filler neck and locked. A lock-controlled bolt member mounted for rotation with the shell is movable by the lock to a cap-removal position. The bolt member engages driving teeth provided within the closure member. The driving teeth are formed such that rotation of the shell in the cap-advancing direction, after the lock has been returned to the cap-locking position, cams the bolt out of engagement with the driving teeth.