Ignition Coil: Description and Operation

HEI Distributor With External Coil:

Wiring Diagram For Engine No Start:

This ignition system uses an external ignition coil. The external coil is mounted remote from the distributor and is connected to the rotor through a high tension coil wire.

The coil is a transformer which steps up battery voltage (12 volts) to high voltage (25,000 to 35,000 volts). The primary circuit is energized when the ignition switch is in the "ON" position. When the ignition module breaks the circuit to ground, on the primary (negative side of coil) circuit, the magnetic field collapses, which induces high voltage in the secondary circuit, which finds its ground at the spark plug.