Distributors & Ignition Systems - DUCELLIER Electronic Ignition: Operation
The distributor contains a trigger plate that turns with the distributor shaft. See Fig 1. The impulse sender coil or coils are located inside the distributor housing. The main coil is located near the vacuum diaphragm, and on dual pick-up models, a secondary coil is located directly opposite (offset 3° for proper ignition timing during warm-up).
On dual pick-up models, 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), a relay switches operation to the main impulse sender. Ignition timing returns from 6° to 3° BTDC. The 2 impulse senders never operate at the same time.
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 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.