Distributor: Description and Operation

Distributor Assembly:

The distributor, mounted to the left front side of the engine, directs high voltage ignition coil output to the spark plugs in proper sequence (firing order). To accomplish this, a rotor on the driven shaft acts as a rotary contact, directing ignition coil voltage to each spark plug terminal as it turns inside the distributor cap.

Inside the distributor, a pick-up coil/igniter assembly is mounted to the breaker plate. A signal rotor on the driven shaft turns past the pick-up coil, triggering the igniter to interrupt the coil primary ground connection each time a spark plug is to fire. A separate pick-up coil generates a "G" signal utilized by the ECU in calculations for fuel injection timing.

Two mechanisms control spark advance. A vacuum diaphragm, mounted on the side of the distributor and connected to the breaker plate with an operating rod, advances timing according to engine load sensed as manifold vacuum. To advance timing with relation to engine speed (rpm), the distributor incorporates a centrifugal advance device. As engine speed increases, two governor weights controlled by calibrated springs are forced to move outward, causing the rotor shaft to move ahead of the main distributor shaft and advance the timing.