Engine Electrical Introduction
The engine is the power source of a vehicle. It burns the mixture of fuel (gasoline) and air and converts its heat energy into the mechanical energy. The air-fuel mixture is first compressed in the engine and then ignited by the spark plug ignition. To start this process, the crankshaft must first be rotated by the external force. These actions are performed by the engine electrical system. It consists of battery, starting system, charging system, and ignition system.
Starting System
The starting (or cranking) system comprises a battery, a starter, and an ignition switch. When the ignition switch is turned to the START (III) position, the starter begins cranking the engine using power from the battery. The starter turns the crankshaft and reciprocates the pistons in order to compress the air-fuel mixture; this action is continued until the crankshaft starts rotating the engine by itself. In the case of vehicles with an automatic transmission, an A/T gear position switch is provided so that the supply of current to the starter can be cut off if the shift lever is in any position other than P (Parking) or N (Neutral), thus preventing the vehicle from starting abruptly. Also, on some manual transmission models, a starter cut relay is provided for the same purpose. The starter in such a configuration cannot be operated without the clutch pedal being depressed.
- A/T gear position switch
- Ignition switch
- Starter cut relay
- Starter
- Battery
The ignition system with distributor comprises a distributor, ignition wires, and spark plugs. A high-voltage current, which is created by the ignition coil inside the distributor, is supplied to the spark plugs via the ignition wiring in order to ignite the air-fuel mixture in the combustion chambers. The distributor both regulates the current and ensures that it is directed to the correct spark plug at the correct time.
Direct Ignition System
The direct ignition system consists of ignition coil relay, ignition coils, spark plugs and
ignitors. Ignitors are built in the ignition coils. When the engine (powertrain) control module
sends ignition signal to a ignition coil, it sends a high voltage to a spark plug to ignite the airfuel mixture.
Charging System
The charging system comprises an alternator, an alternator belt, a charging system light and
a battery. The alternator, which is driven by the crankshaft via the alternator belt, generates
electricity while the engine is running, thus charging the battery and supplying power to all of
the vehicle’s electrical systems. The charging system light informs the driver whenever a
problem arises with the charging system.
Precautions When Handling the Electrical System
- Before starting the service, be sure to disconnect the negative terminal of the battery. (When the battery negative terminal is removed, the memory of the radio stations are erased. Record the memorized stations before disconnecting the terminal.)
- After the service, check the connection, installation condition and routing of the harness.
- If both the battery terminals are disconnected, connect the positive terminal first.