Starting System Circuit Description (LG5 Engine)

Starting System Circuit Description (LG5 Engine)

Battery voltage is available at the ignition switch at all times through CKT 642 (RED) from Maxifuse(R) block 2. Battery voltage is available to the starter relay contacts at all times through the CKT 2 (RED) from fusible link M off of the starter. Placing the ignition switch in the START position closes the contacts in order to apply voltage on CKT 5 (YEL) to the neutral switch (automatic transmission). If the automatic transmission is in the NEUTRAL position, voltage applies to CKT 434 (ORN/BLK) to the starter relay coil. CKT 150 (BLK) grounds the starter relay coil at ground G401. The starter relay energizes when the voltage applies to the coil. Voltage then applies to the starter solenoid winding terminal S through CKT 6 (PPL). Battery voltage is also available at all times through CKT 1 (BLK) at starter solenoid terminal B.

Current flows through the hold-in winding to the mechanical ground at the solenoid when the battery voltage applies at the starter solenoid terminal S. Simultaneously, current flows through the pull-in winding and the starter motor to the starter motor's mechanical ground. The combined force of these windings performs the following actions:

* Overcomes the combined force of the return spring.
* Pulls the starter's plunger in order to engage the starter with the flywheel drive assembly through the shift lever.

The engine starts to turn over. The plunger actuation also operates a contact in the starter solenoid. This contact closes in order to apply battery voltage directly tot the starter motor. The pull-in winding no longer has a voltage drop across the coil when the battery voltage applies directly to the starter motor. The current ceases to flow. The starter solenoid remains engaged due to the current flow through the hold-in winding alone.

The starter motor continues to operate until the ignition switch returns to the RUN position. Voltage is removed from the starter solenoid terminal S when the ignition switch remains in the RUN position. Voltage still remains at the BAT terminal. Battery voltage from CKT 1 (BLK) energizes both the hold-in winding and the pull-in winding. The forces from these windings now oppose one another. The plunger returns to the disengaged position through the operation of the return spring. This action operates the contact in order to remove battery voltage from the starter motor and the motor stops. Both windings also de-energize. This plunger operation also retracts the starter form the flywheel drive assembly. The engine operates on the engine's own power. Some vehicles are equipped with a starter thermal switch. The starter thermal switch opens the crank signal line when the starter temperature exceeds 140°C (285°F). This action prevents overheating the starter motor.