How a Car Starter Motor Works

2025-09-05

Startup phase
Press the start switch → The electromagnetic switch is energized → The drive gear engages with the flywheel ring gear → The DC motor begins to rotate → Torque is transmitted to the engine crankshaft → Once the engine reaches its starting speed, it continues running on its own.
Stop phase
After the engine starts → the electromagnetic switch cuts power → the return spring pulls back the drive gear → and the starter motor stops operating.
Key parameters
Gear ratio: Gasoline engines typically range from 13 to 17, while diesel engines operate between 8 and 10, helping to increase torque and reduce starting resistance.
Current characteristics: At startup, the current spikes dramatically—reaching up to hundreds of amperes—requiring the battery to deliver high-power support.

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