Starter motors refer to electric motors that provide rotation for internal combustion engines to start the engine. Starter motor failure, which results in failure to start the engine, can occur for numerous reasons.
Starter motors rely on commutators, or switches that reverse the direction of current between the external circuit and rotor, to contact the motor's brushes and generate electrical power. Commutators can wear down over time, or accumulate dirt or other sediment that can impede operation. Cleaning or replacing the commutator typically corrects the problem.
Motor bearings, or devices in a motor that allow rotational movement between parts, can also fail due to normal wear and tear. Worn bearings can cause the armature, or coil that generates electrical energy via a magnetic field, to drag on the stator, or stationary component of the motor, resulting in a short circuit and starter motor failure. Replacing the bearings typically restores normal motor function.
A jammed Bendix gear, or gear used to press into the flywheel ring gear to crank the engine, often results in a "clunking" noise when attempting to start the engine. The jammed Bendix gear, along with the ring gear and, if damaged, the starter motor, may need replacement to start the engine.