System Overview
This documents describes the principles of starter motor, irrespective of the make.
The purpose of the starter motor (6/25) is to turn the engine at start-up. The starter motor is positioned on the cylinder block side towards the transmission. A solenoid forces a pinion to engage with the gear ring on the flywheel / carrier plate of the engine. When the engine starts and the engine speed exceeds the starter motor speed, the pinion disengages. This prevents the starter motor over-revving.
This type of starter motor is equipped with permanent magnets instead of field winding.
The starter motor gives the greatest torque at low RPM at the same time as the voltage flow through the starter motor is greatest.
The engagement time for the starter motor must not exceed 20-30seconds. Longer engagement time may result in the starter motor overheating and becoming damaged.
A starter motor relay (2/35) controls the starter motor solenoid. The ignition switch (3/1) and engine control module (ECM) (4/46) control the relay. The ignition switch powers the relay and the engine control module (ECM) grounds it.
On vehicles with four-cylinder engines and automatic transmissions the starter motor relay is controlled by both the ignition switch (3/1) and Engine control module (ECM) (4/46), where the ignition voltage feeds the relay and Engine control module (ECM) grounds the relay when the gear selector is in position P or N. When the gear selector is in position N it is also required that the brake pedal is depressed.