Ignition System: Description and Operation

Fig. 5 Ignition Control System.:

When the ignition key is turned on voltage is present at the primary circuit of both ignition coils. As the distributor shaft rotates the teeth of the reluctor first pass the leading pickup coil generating a signal which is passed to the leading electronic control module (igniter). The igniter then breaks the circuit in the primary winding of the leading ignition coil. The resulting colapse of the magnetic field surrounding the primary and secondary windings of the coil induces a voltage in the secondary winding which fires the leading spark plug.

As the distributor shaft continues to rotate, the reluctor teeth pass the trailing pickup coil, generating a signal which is passed to the trailing electronic control module (igniter). The igniter then breaks the circuit in the primary winding of the trailing ignition coil. The resulting colapse of the magnetic field surrounding the primary and secondary windings of the coil induces a voltage in the secondary winding which fires the trailing spark plug. The resulting one-two firing of the leading/trailing spark plugs results in more complete and efficient burning of the combustion charge thereby reducing emissions.

An emission control unit also slightly modifies the ignition timing based on engine load to further reduce emissions.