Ignition System: Description and Operation

The ignition system consists of a Single Module Engine Controller (SMEC) and its sensors, ignition coil, and distributor that sends crankshaft and camshaft position information to the SMEC as well as distributing coil secondary output. The Single Module Engine Controller (SMEC) controls the entire ignition system. It gives the capability of igniting the fuel mixture according to different engine conditions during engine operation by delivering a variable electronic spark advance curve. The SMEC has a built in microprocessor that continually receives input from the engine monitoring sensors. The computer then electronically advances or retards the ignition timing to provide good driveability during operation. During the CRANK-START period the SMEC will provide a set amount of advanced timing to assure a quick efficient start. The amount of electronic spark advance provided by the SMEC is determined by three input factors, coolant temperature, engine rpm, and manifold vacuum. The SMEC also receives information from the oxygen sensor and electronically adjusts the air-fuel mixture to assure the most efficient fuel burn possible. The SMEC also controls the Auto Shut-Down (ASD) Relay, which controls power to the ignition coil, fuel pump, oxygen sensor heater element, and fuel injectors. On turbo equipped vehicles the distributor contains an additional sensor used for fuel injection timing.