Starting System: Description and Operation

STARTER SYSTEM
The starting system cranks the engine at a speed fast enough to permit the engine to start.
^ Heavy cables, connectors and switches are used because of the large current required by the starter motor while it cranks the engine.
^ The amount of resistance in the starting circuit must be kept to a minimum to provide maximum current for starter motor operation.
^ A discharged or damaged battery, loose or corroded connections or partially broken cables will cause slower than normal cranking speeds and may prevent the starter motor from cranking the engine.

For starting system concerns:
^ The operator may have discharged the battery before calling for assistance.

The starting system includes:
^ The permanent magnet gear-reduction starter motor with a solenoid-actuated drive
^ The battery
^ A remote-control starter switch (part of the ignition switch)
^ The transmission range (TR) sensor
^ Starter interrupt relay
^ Heavy circuit wiring
^ A starter solenoid
^ The steering column/ignition/lighting control module The Transmission Range (TR) sensor prevents operation of the starter motor unless the selector lever is in the NEUTRAL or PARK position.

Sequence of Operation
1. Battery positive voltage is constantly supplied to the starter interrupt relay normally open contact through the power distribution box maxifuse 27 (30A).
2. The ignition switch is turned to START, sending a start signal to the steering column/ignition/lighting control module and supplying voltage to the high side of the starter interrupt relay coil through fuse junction panel Fuse 6 (10A).
3. The steering column/ignition/lighting control module will ground the coil of the starter interrupt relay if:
^ the keycode matches the code stored in memory.
^ the engine rpm does not exceed 200 rpm.
^ the transmission range sensor is in PARK or NEUTRAL.
4. A magnetic field is created in the starter interrupt relay, closing the contact points and supplying voltage to the starter solenoid.
5. The iron plunger core is drawn into the solenoid coil.
6. A lever connected to the starter drive engages the drive pinion gear to the flywheel ring gear.
7. When the iron plunger core is all the way into the coil, its contact disc closes the circuit between the battery and the starter motor terminals.
8. The current flows to the motor and the starter drive cranks the flywheel and the crankshaft.
9. As current flows to the motor, the solenoid pull-in coil is bypassed.
10. The hold-in coil keeps the starter drive engaged with the flywheel.
11. The starter drive remains engaged until the ignition switch is released from the START position.

An over running clutch in the starter drive protects the starter motor from excessive speeds during the brief period before the driver releases the ignition switch from the START position (as the engine starts).