It is often thought that when a fire is found in parked motor vehicles, the fire may occur after an engine stops. Also, it is easy to judge that when motor vehicle fires occur during engine stopping, it may be caused by arson or electrical causes irrespective of a fuel system. This study analyzed motor vehicle fires which occurred in operation but were found after parking and revealed that these fires were caused by the defect of a fuel system and the same motor vehicle types had fires by the same causes. Moreover, this study provided judgement process of major fire causes and periods for fire investigators to apply when investigating fires of parked motor vehicles. And this fire is related to automotive products liability.