Distributor: Description and Operation

Distributor Assembly:

PURPOSE
Directs high voltage ignition coil output to spark plugs in proper sequence (firing order). 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.

LOCATION
Left front of engine.

OPERATION
Inside the distributor, a trigger wheel with "windows" in its side rotates with the distributor shaft. An LED and a photosensor are mounted on the inside and outside of the trigger wheel. As the windows of the wheel pass between the LED and sensor, a signal is created that the ECU "reads".

Spark timing is computer controlled. The ECU monitors this signal and uses it to calculate engine speed and crankshaft position. The ECU then compares this information with signals from other sensors to determine ignition timing.