Ignition System: Description and Operation

Ignition Coil And Module Assembly:

PURPOSE
The Integrated Direct Ignition System (IDIS) is designed to replace the mechanical distributor (HEI) in producing and controlling secondary coil voltage.

CONSTRUCTION
The Integrated Direct Ignition System (IDIS) consists of two separate ignition coils, an ignition module and a secondary conductor housing mounted to an aluminum cover plate. A crankshaft sensor, related connecting wires and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM), make up the remainder of the system. The coil and module assemblies are located under the ignition cover and are connected to the ECM by an 11-pin connector. This system dose not use any spark plug wires because the coils are mounted directly on top of the spark plugs.

OPERATION
The ignition module controls the primary circuit to the coils, turning them "ON" and "OFF." It also controls spark timing below 700 rpm and if the ECM bypass circuit becomes open or grounded. The ignition module also monitors the crankshaft sensor signal, using it to send a reference signal to the ECM which in turn maintains correct spark and fuel injector control under all driving conditions.

This system uses Electronic Spark Timing (EST) and control wires from the ECM, as with distributor systems. The ECM controls timing using crankshaft position, engine rpm and engine temperature, and manifold absolute pressure (MAP) sensing.

Ignition Current Flow:

This system uses the "Waste Spark" method of spark distribution. Each cylinder is paired with its opposing cylinder in firing order so that one cylinder on the compression stroke fires simultaneously with its opposing cylinder on the exhaust stroke. Requiring less voltage to fire the plug on the exhaust stroke, most of the available voltage is sent to the compression stroke cylinder. This process is reversed as the cylinders' roles are reversed.