Distributors & Ignition Systems - DUCELLIER Electronic Ignition: Operation
The distributor contains a trigger plate that turns with the distributor shaft. See Fig 1. Two impulse sender coils are housed in the distributor - the main coil near the vacuum diaphragm and the secondary coil directly opposite (offset 3° for proper ignition timing during warm-up).
When oil temperature is below 59° F (15° C), the secondary impulse sender operates to provide 3° additional advance (6° total). When oil temperature reaches 59° F (15° C) or higher, a relay switches operation to the main impulse sender which takes over the function from the secondary. Ignition timing returns from 6° to 3° BTDC. The two impulse senders never operate simultaneously.
As the rotating trigger plate approaches and passes the proper 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 coils, terminal "G" through a relay switch that activates either the main or secondary 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.