Distributors & Ignition Systems: Operation

As the distributor shaft turns, a reluctor rotates inside a pick-up coil assembly. As the reluctor teeth pass the pick-up coil, a signal is generated similarly to that produced by a small magneto generator.

The signal is produced in exact synchronization with distributor shaft rotation, four times per rotation and at equally spaced intervals.

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

The centrifugal advance mechanism is located below the rotor assembly. 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. This too advances ignition timing.