 This causes the starter solenoid to close a pair of heavy contacts, thus relaying a large electric current through the starter motor, which in turn sets the engine in motion.The starter motor is a series, compound, or permanent magnet type electric motor with a solenoid and solenoid operated switch mounted on it.When low-current power from the starting battery is applied to the starter solenoid, usually through a key-operated switch, the solenoid closes high-current contacts for the starter motor and it starts to run.