Air carrier Captain reported that a passenger had brought a prohibited engine component onboard which was emitting fuel odor during cruise.

Narrative

Passenger was improperly allowed to board with restricted item (engine component) in carryon baggage. FA (Flight Attendant) noticed the smell of fuel as we reached cruise altitude. Did not leak fuel or have any liquid fuel in it but the odor required FAs to move it to a galley cart. Because there was no volatile liquid and just an odor; I made the decision to forgo an overweight diversion to ZZZ1. I did review volatile liquid and odor QRH procedures. FAs and cockpit stayed in communication as we continued to ZZZ. Dispatch and ZZZ GSC (Ground Security Coordinator) team notified. Cause: I would recommend more FOM guidance on what to do when a restricted item is discovered in flight. Other than that it appears it was the station in ZZZZ or ZZZZ airport security that allowed the passenger on board with this component as a carryon.