1. Power Supply: The battery provides the initial electrical power.
2. Ignition Switch: Turning the ignition key (or pressing the start button) completes a circuit, allowing power to flow.
3. Ignition Coil: This is a transformer that steps up the relatively low voltage from the battery (typically 12 volts) to a much higher voltage (tens of thousands of volts). This high voltage is necessary to jump the gap in the spark plug.
4. Distributor (Older Systems): In older vehicles with distributors, the distributor has a rotating cam that opens and closes the points (or uses a hall effect sensor in electronic ignition systems) to send the high voltage to the correct spark plug at the precisely timed moment. The timing is crucial for optimal combustion. Modern engines typically don't use a distributor.
5. Ignition Control Module (ECM/PCM): In modern vehicles, an Engine Control Module (ECM) or Powertrain Control Module (PCM) – the car's computer – controls the ignition timing with extreme precision. It uses various sensors (like crankshaft position sensor and camshaft position sensor) to determine the optimal ignition timing based on engine speed, load, and other factors. The ECM/PCM signals a switch to send the high voltage to the correct spark plug.
6. Spark Plugs: The high-voltage electricity from the coil travels through the ignition wires (or coil-on-plug systems) to the spark plugs. The spark plug has a gap between its electrodes. The high voltage creates a spark across this gap, igniting the compressed air-fuel mixture in the cylinder.
7. Combustion: The burning of the air-fuel mixture creates a controlled explosion that pushes the piston down, turning the crankshaft and ultimately powering the vehicle.
Coil-on-Plug (COP) Systems (Modern Engines):
Most modern vehicles use a Coil-on-Plug (COP) system. In this system, each cylinder has its own ignition coil mounted directly on top of the spark plug. This eliminates the need for a distributor and high-voltage wires, improving reliability and performance. The ECM/PCM still controls the timing of the spark, but the signal goes directly to the individual coils.
In short, the ignition system takes low-voltage battery power, boosts it to a very high voltage, and precisely times the delivery of that voltage to the spark plugs to ignite the air-fuel mixture, thereby starting and running the engine.
