Distributor: Description and Operation

Distributor Assembly:

The distributor, mounted to the left end of the cylinder head and driven by the camshaft, 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.

The distributor utilizes a photo-diode type crank angle sensor consisting of a slotted disc that turns with the distributor shaft and a stationary pick-up assembly. As the disc rotates past the pick-up, the slots (one for each cylinder) alternately pass and block photo-diode light transmission. Signals generated are interpreted by the ECU to determine crank angle (#1 cylinder TDC) and engine rpm. To calculate ignition timing, the ECU uses this input together with several others related to vehicle operating conditions. Except for the initial setting, ignition timing is under ECU control.