MOTORCRAFT Solid State Ignition (SSI): Operation
The ECU and ignition coil are turned on whenever the ignition switch is in the "START" or "ON" position. When the engine begins turning the distributor shaft, the trigger wheel rotates with it.
As each tooth passes the sensor, it interrupts the magnetic field around the sensor. This continual buildup and collapse of the field provides a signal to the ECU.
The ECU receives this signal, and turns the power to the ignition coil's primary circuit off and on as each tooth passes the sensor.
A third connector is used on models with 6-cylinder engines and electronic feedback system.
The collapse of the magnetic field in the ignition coil primary circuit induces a high voltage surge in secondary, causing current to flow from the coil to the distributor, rotor, cap and spark plug wires.