Electronic Control Unit

The electronic control unit is located in a metal housing on the firewall. A switching transistor is exposed on top for more efficient cooling. The control unit is connected to the rest of the system by a wiring harness and a 4-wire connector. The control unit functions whenever the ignition switch is turned to the "START" or "RUN" positions.

In the "START" position, it furnishes current through the dual pick-up start-run relay, to the start pick-up in the distributor. In the "RUN" position, it furnishes current through the switched relay to the distributor's run pick-up.

The signal created, as the reluctor teeth pass the "live" pick-up coil, is transmitted by the control unit to the primary circuit of the ignition coil. As current to the primary is cut off, the magnetic field there collapses, causing a voltage surge in the secondary windings. This fires the spark plugs.

The length of time current is permitted to flow through the coil's primary circuit (dwell time) is determined by the control unit and is not adjustable.