DS III

Ignition System Schematic:

The Dura Spark III system is used on vehicles equipped with Electronic Engine Control (EEC) III. The system consists of a primary side consisting of the battery, ignition switch, primary circuit, EEC system input and ignition module, Fig. 2, and a secondary side consisting of distributor cap, rotor, spark plug wires and spark plugs. When the ignition switch is in the On position, the primary circuit and the ignition coil are energized. The EEC system provides a signal which tells the ignition module to turn off the coil primary circuit. The off and on times of the primary circuit are controlled by the EEC computer. When the circuit is turned Off, the magnetic field built up in the ignition coil collapses, inducing a high voltage into the coil secondary windings. This high voltage is then delivered to the spark plugs by the secondary ignition wires.

Fig. 1 Typical Dura Spark III ignition system:

The control module has no purple wire (Dura Spark II) and can be distinguished by the brown sealing block or grommet, Fig. 1.
Ignition timing is determined by the crankshaft position sensor (CP) and several other EEC related sensors which feed information to the Electronic Control Assembly (EEC processor) through the 32 pin connector.
The various input sensors are (depending on if the vehicle is carbureted or fuel injected), the exhaust gas oxygen (EGO), engine coolant temperature (ECT), EGR valve position (EVP), throttle position (TP), barometric manifold absolute pressure (BMAP), and air charge temperature (ACT) sensors.