Ignition System - MITSUBISHI Electronic: Operation

As the distributor shaft turns, a reluctor rotates inside the pick-up coil assembly. As reluctor teeth pass the pick-up coil, a signal is generated similar to that produced by a small magneto generator. The signal is produced in synchronization with distributor shaft rotation, 4 times per rotation and at equally spaced intervals.

The signal generated is sent to the IC igniter. The igniter switches current on or off in the ignition coil primary circuit. As current is shut off, the magnetic field in the coil primary circuit collapses. This results in a voltage surge in the secondary circuit, firing the appropriate spark plug.

The centrifugal advance mechanism is located under the rotor. As engine speed increases, the weights move outward, causing the reluctor to rotate ahead of the distributor shaft, advancing timing.

The vacuum advance has a spring-loaded diaphragm connected to the breaker assembly. As engine vacuum increases, the diaphragm pivots the movable breaker assembly in a direction opposite to shaft rotation, advancing ignition timing.