Which starter motor component engages the flywheel during the starting sequence?

The pinion gear is the component of the starter motor that engages the flywheel during the starting sequence. When the ignition is turned, the starter motor is activated, and the pinion gear extends and meshes with the flywheel's ring gear. This engagement is critical as it allows the starter motor to turn the engine over, initiating the combustion process necessary for starting the vehicle.

The starter housing serves to protect and encase the internal components of the starter motor but does not play a direct role in engaging the flywheel. Brushes provide electrical contact and help transmit power from the battery to the rotating armature within the starter motor but do not engage with the flywheel. The crank relay is an electrical component that enables the flow of current to the starter motor, but it does not interact with the flywheel. Thereby, the function of engaging the flywheel squarely falls on the pinion gear, making it the essential part in the starter motor assembly for starting the engine.