Ignition Coil: Description and Operation

Ignition Coil Pack Showing Plug Wire Locations:

Ignition Current Flow:

DESCRIPTION
The ignition coils are transformers that convert the low primary ignition voltage into the high secondary ignition voltage required to produce a spark at the spark plugs. Four twin tower ignition coils are combined into a single coil pack unit. This unit is mounted to the engine below the ignition module (under the intake plenum). The ignition system uses a waste spark method of spark distribution. Each of the four coils fires two cylinders at once. One cylinder is on the compression cycle, while the other is on the exhaust cycle.


OPERATION
The ignition coils get battery voltage when the ignition is turned "ON" and current flows through the primary circuit when the ignition control module coil driver is grounded. When a spark is needed, the ignition module opens the primary circuit, breaking the circuit to ground. The sudden change in magnetic field surrounding the secondary coil windings induces a high voltage in the secondary circuit. When this voltage is high enough to "push" through the resistance of the secondary circuit and cross the air gap at the spark plug, a spark is produced. Since less energy is required to fire the spark plug in the cylinder on its exhaust stroke, the plug on the firing stroke determines the discharge voltage required to create a spark.