An electric starter motor works by generating a heavy electric current at high speeds to turn and start an engine. The starter motor is equipped with a large electric switch that turns on and then off automatically in a short period of time. The electric switch is made to withstand high currents from a car battery and combines with a solenoid valve and electromagnet to start the engine.
The electromagnet is essential to complete the electric circuit, which then draws an iron rod to connect the car battery and the engine starter. This iron rod is fitted with a return spring so that the connection between the starter motor and the engine is not longer than it has to be. If an engine and a starter motor are connected for too long, the excessive spinning from the engine may damage the starter motor.
The electric starter motor is essential in starting up a modern engine, as it needs to be turned at high speeds. Once the engine has started turning, it can begin operation by filling the cylinders with air and fuel and then compressing it. In cars where the engine is mounted at the front, the starter motor can be found near the back of the engine, mounted low.