Starter Motor: Description and Operation

Fig. 1 Exploded View Of Starter Motor Assembly:

The armature is connected to the starter drive pinion shown in Fig. 1. As the armature moves forward from the magnetic field of the pull-in coil, the starter drive pinion is moved toward the flywheel. At the end of its travel, the starter drive pinion engages with the flywheel. Once the starter drive pinion and flywheel are fully engaged, the contact disc completes the circuit between the B and M terminals and the armature rotates. A hold-in coil is energized by the S-terminal, to supply he additional magnetic force required to keep the contact disc engaged as the starter draws current and the system voltage drops.