Starting the engine is possibly the most important function of the vehicle's electrical system. The starting system performs this function by changing electrical energy from the battery to mechanical energy in the starting motor. This motor then transfers the mechanical energy, through gears, to the flywheel on the engine's crankshaft. During cranking, the flywheel rotates and the air-fuel mixture is drawn into the cylinders, compressed, and ignited to start the engine. Most engines require a cranking speed of about 200 rpm.

Two different starting systems are used on Toyota vehicles. Both systems have two separate electrical circuits ... a control circuit and a motor circuit. One has a conventional starting motor. This system is used on most older-model Toyotas. The other has a gear reduction starting motor. This system is used on most current Toyotas. A heavy-duty magnetic switch, or solenoid, turns the motor on and off. It is part of both the motor circuit and the control circuit.

Both systems are controlled by the ignition switch and protected by a fusible link. On some models, a starter relay is used in the starter control circuit. On models with automatic transmission, a neutral start switch prevents starting with the transmission in gear. On models with manual transmission, a clutch switch prevents starting unless the clutch is fully depressed. On 4WD Truck and 4-Runner models, a safety cancel switch allows starting on hills without the clutch depressed. It does so by establishing an alternate path to ground.



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