Engaging the pinion

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Fig 1: Engaging Pinion

Courtesy of VOLVO CARS OF NORTH AMERICA.

When the ignition key is turned to position II, the starter motor relay is supplied power at position 86. If the immobilizer check is OK, the central electronic module (CEM) or engine control module (ECM) supply the relay with a ground connection at position 85 and the relay is activated. Depending on the type of engine management system, the starter motor relay is regulated by either the central electronic module (CEM) or the engine control module (ECM).

Solenoid position #2 (50) is supplied power from relay position 87. This creates a magnetic field in both the pull-in and hold-in winding. This generates a movement of the moving steel core. When the core moves, a lever fixed to the end of the core causes the starter motor 's pinion to mesh with the crown wheel on the flywheel/carrier.

The pull-in winding is grounded through the rotor and carbon brushes. This ground connection is lost when the moving switches close the circuit and the current passes from the solenoid to the starter motor.