Ignition System: Description and Operation

PURPOSE
The automotive ignition system is designed to:
- Increase battery voltage to 20,000 volts or more.
- Distribute voltage to the spark plugs.
- Ignite the air fuel mixture.

OPERATION
When the ignition key is turned on, battery voltage is supplied to the positive side of each ignition coil's primary winding. As the engine begins to turn, the Crankshaft Position Sensor (CKPS) determines the engine rpm and crankshaft position;The CKPS then sends this information to the Engine Control Module (ECM).

The ECM takes the information, based upon a map programmed into the Read Only Memory (ROM) and supplies a pulsed ground signal to the base of the power transistor. The power transistor cuts the voltage to the primary windings in the ignition coils. This causes the magnetic field surrounding the primary windings to collapse and a voltage surge is created in the secondary windings of the ignition coils.

High voltage flows out of each coil directly to its respective spark plug. The voltage spike jumps the gap at the spark plugs' electrodes completing the path to ground, igniting the fuel mixture.