Ignition System - Direct: Description

The Direct Ignition System (DIS) eliminates the need for the conventional distributor. The DIS ignition system consists of 2 or 3 separate ignition coils, a DIS ignition module, a crankshaft position sensor, wiring harness and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM).

This system utilizes the EST signal from the ECM to control spark timing. Ignition timing is controlled by the ECM, using information from the following inputs: crankshaft position, engine RPM, engine temperature, engine load (manifold pressure or vacuum), air temperature and atmospheric pressure.

In the direct ignition system, each cylinder is paired with the cylinder opposite it in the firing order. On 2.8L engines, cylinders No. 1-4, 3-6 and 2-5 are paired together.

The spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming down on the exhaust stroke. The process is repeated when the cylinders reverse roles. Each cylinder pair is fired by its own ignition coil.