Ignition System - 2.5L/3.9L/5.2L: Operation

The SMEC has 2 functional modes, start and run. Start mode functions only during engine cranking and starting. Fixed amount of spark advance is provided, based on distributor position.

Run mode functions only when engine starts and is operating normally. Hall Effect pick-up assembly and 3 sensors provide information to SMEC, which varies spark advance to match engine operating conditions. Spark timing and dwell cannot be adjusted in start mode.

If computer run mode fails, system will go into start mode. This enables the vehicle to be driven in for repair. Performance and fuel economy will be poor while operating in start mode. If the Hall Effect pick-up or start mode of the computer fails, engine will not start or run. If no ignition signal is present with the key in "RUN" position, the Auto Shutdown (ASD) relay will interrupt power to the electric fuel pump, fuel injectors and ignition coil.