Ignition Coil: Description and Operation

PURPOSE

The ignition coil is a component of the ignition system that is used to produce a voltage strong enough to jump the spark plug gap and ignite the air/fuel mixture under all operating conditions.


CONSTRUCTION

The ignition coil consists of a primary winding, a secondary winding, and a soft iron core. The windings are embedded in an epoxy compound to protect the coil from vibration damage.

The primary windings are made up of 2-3 hundred turns of heavy gauge wire, over the secondary windings. The secondary windings are made up of 20-30 thousand turns of light gauge wire around a soft iron core.


OPERATION

Ignition Coil Operation (Coil Construction May Vary):

Power is supplied to the positive side of coil by the ASD relay. Switching of the negative coil ground is controlled by the engine controller.

When the engine controller grounds primary circuit, current flows through the primary windings, and a magnetic field is produced. As the magnetic field builds it is concentrated in the soft iron core.

When the engine controller opens the primary circuit ground, the magnetic field collapses. As the field collapses it passes through each turn of the secondary windings, producing a small voltage in each turn. The voltage in each turn is multiplied by the number of wire turns.