starter

An automobile starter assembly. The larger cylinder is the motor housing, and the smaller cylinder on top is the solenoid which controls power to the motor and engages the drive pinion with the engine's flywheel.

A starter (also self-starter, cranking motor, or starter motor) is an apparatus installed in motor vehicles to rotate the crankshaft of an internal combustion engine so as to initiate the engine's combustion cycle. Starters can be electric, pneumatic, or hydraulic. The starter can also be another internal combustion engine in the case, for instance, of very large engines, or diesel engines in agricultural or excavation applications.