Ignition System - Non-Turbo: Operation

The distributor contains a trigger plate that turns with the distributor shaft. See Fig 1. The impulse sender coil is located inside the distributor housing. The coil is located near the vacuum diaphragm.

Fig 1: Internal Distributor Components To adjust gap, trigger plate arm must be aligned with stud on impulse generator.

As the rotating trigger plate approaches and passes the impulse sender coil, a magnetic field builds and collapses, sending a signal to the electronic control unit. This signal opens and closes a transistor in the electronic control unit, turning the primary circuit in the ignition coil on and off.

When the primary coil circuit is turned off, a high voltage surge occurs in the coil secondary circuit, providing spark to the spark plugs through the distributor rotor, cap and secondary wires.

The electronic control unit has 4 terminals. See Fig 2. Terminals "W" and "G" are connected to the distributor impulse sender coil.

Terminal "B" is connected to the coil positive terminal and terminal "C" to the coil negative terminal. The unit is grounded, through one of its mounting bolts, to the support shared with the ignition coil.

Fig 2: Electronic Control Unit Terminals Note size of terminal "G."