System Description

The Computer Controlled Coil Ignition (C3I) system consists of a camshaft sensor, crankshaft position sensor, the Electronic Spark Timing (EST) portion of the ECM, an ignition module, three ignition coils, in a one piece unit called a coil pack, and the related connecting wires.

The camshaft sensor sends a signal to the ECM which uses it as a "sync pulse" to trigger the injectors in proper sequence. The cam signal is passed through the ignition module. It is not processed in any way.

The crankshaft sensor sends a signal through the ignition module to the ECM. The ECM uses this reference signal to calculate engine speed and crankshaft position.

In much the same manner as the distributor type ignition system, this system uses the EST signal from the ECM. Above 450 rpm, the ECM applies 5.0 volts to the ignition module (bypass circuit) signaling the module to allow the ECM to control the dwell and spark timing. This is called EST mode. During EST mode, the ECM compensates for all driving conditions.

Ignition Current Flow:

Three separate coils are mounted to the module assembly. Each coil provides the spark for two plugs simultaneously. Each coil can also be replaced separately. A "Waste Spark" method of distribution is used on this system. 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.

The ignition module controls spark timing under 400 RPM and must receive a "sync-pulse" followed by a Crank Signal in that order to enable engine start up. The ignition module monitors the crankshaft sensor signals and based on these signals, sends a reference signal to the ECM to allow the correct spark and fuel injector control to be maintained during all driving conditions.