CASING SUB ASSY. G25421270 - Caterpillar

Illustration 1 g00546881
Simplified Schematic for the Starting and Stopping of the EngineThis circuit starts the engine and this circuit also stops the engine. When the key start switch is placed in the START position with the left console in the DOWN position, no current flows to the starter relay and the engine does not start.When the key start switch is placed in the START position with the left console in the UP position, there is current flow through the starting/pilot enable switch to the start relay. After the start relay contact closes, current flows to the starter solenoid.As the starter solenoid is energized, current flows from the "MTR" terminal of the starter solenoid to the "START" terminal of the shutdown solenoid. The start coil in the shutdown solenoid energizes and the fuel rack is moved into the OPEN position. The plunger in the starter solenoid will extend and the pinion gear for the starting motor will operate.The pinion gear engages with the ring gear of the flywheel in order to start the engine. Releasing the key start switch to the ON position de-energizes the starter solenoid. The plunger within the starter solenoid returns to the retracted position and the starting motor is deactivated. The solenoid is latched and the fuel rack stays in the OPEN position while the shutdown solenoid is deactivated. When the key start switch is moved to the OFF position, there is current flow through the start/stop relay to the "STOP" terminal of the shutdown solenoid. The stop coil in the shutdown solenoid is energized and the fuel rack moves to the CLOSE position. Fuel is not supplied to the engine and the engine stops.