MOTORCRAFT EEC III Ignition System: Operation: Notes

With the ignition switch turned on, the primary circuit is on and the ignition coil is energized. See Fig 1. The EEC system (not the distributor as in Dura-Spark II systems) provides a signal telling the ignition module to turn off the coil primary circuit.

Fig 1: EEC III Ignition System Schematic

Courtesy of FORD MOTOR CO.

The length of time the primary circuit is turned on or off is controlled by the EEC Electronic Control Assembly (ECA). See Fig 2. When the current is on, it flows from the battery through the ignition switch, primary windings of ignition coil, and ignition module circuits to ground.

Fig 2: EEC III Electronic Control Assembly

Courtesy of FORD MOTOR CO.

When the current is turned off, the magnetic field which built up in the ignition coil collapses, inducing high voltage to the secondary windings of the coil. This high voltage, produced each time the magnetic field builds and collapses, is transmitted by the coil to the distributor, rotor and cap to individual spark plugs.

The function of the electronic control assembly and engine sensors follows: