Ignition System Description

The 3800 (VIN K) electronic ignition system uses a coil pack. For each two cylinders in the engine, the coil pack uses one ignition coil. The ignition control module (ICM) is mounted under the ignition coils. The ICM performs ignition coil switching functions and interacts with the powertrain control module (PCM) in order to optimize ignition system operation.

The 3800 ignition system spark timing is controlled electronically. The ICM controls the spark timing during engine start-up. The ICM provides a back-up timing system that will allow the engine to run in the event of an open or ground in the ignition control circuit. Once the engine starts and is running above 400 rpm, the PCM takes over the spark timing and sends signals to the ICM for ignition coil switching.

The electronic ignition system uses a waste spark method of spark distribution. Each cylinder is paired with its opposing cylinder in the firing order. One cylinder on compression fires simultaneously with the opposing cylinder on exhaust. The exhaust stroke spark is referred to as the waste spark.

The spark plugs in the two opposing cylinders are connected to the two secondary terminals of the same ignition coil. The spark voltage appears at the center electrode of one of the spark plugs and jumps the side electrode. The spark voltage then passes through the cylinder head to the other spark plug. At the second spark plug, the spark jumps from the side electrode to the center electrode. The spark then completes the series circuit back to the ignition coil. The high level of energy available from the ignition coil fires both plugs simultaneously. Since the waste spark requires very little voltage to fire, the coil output voltage fires the cylinder that is on the compression stroke