Distributor: Description and Operation

Distributor Components:

PURPOSE
The distributor 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.

OPERATION
The distributor uses photo-diode type crankshaft and camshaft position sensors 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 alternately pass and block photo-diode light transmission. Signals generated are interpreted by the ECM to determine camshaft position (#1 cylinder TDC) and engine rpm. To calculate ignition timing, the ECM uses this input together with several others related to vehicle operating conditions. Except for the initial setting, ignition timing is under ECM control.