What’s inside a starter motor, in this video we take a look inside a starter motor to see how it works and the main parts for automotive engineering.The electric starter motor or cranking motor is the most common type used on gasoline engines and small diesel engines.
source/image: The Engineering Mindset
The modern starter motor is either a permanent-magnet or a series-parallel wound direct current electric motor with a starter solenoid similar to a relay mounted on it.
When DC power from the starting battery is applied to the solenoid, usually through a key-operated switch the “ignition switch”, the solenoid engages a lever that pushes out the drive pinion on the starter driveshaft and meshes the pinion with the starter ring gear on the flywheel of the engine.
The solenoid also closes high-current contacts for the starter motor, which begins to turn. Once the engine starts, the key-operated switch is opened, a spring in the solenoid assembly pulls the pinion gear away from the ring gear, and the starter motor stops.The starter’s pinion is clutched to its drive shaft through an overrunning sprag clutch which permits the pinion to transmit drive in only one direction.