Distributor: Description and Operation

PURPOSE/OPERATION
Directs ignition coil output to the spark plugs in proper sequence (firing order). The rotor turns inside the distributor cap acting as a rotary contact sending coil output voltage to each spark plug.

The distributor consists of a housing, shaft, drive gear, distributor cap, rotor, and houses the crankshaft position sensor and the camshaft position sensor. These are photo-diode type sensors using 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 engine control module to determine camshaft position and engine rpm. To calculate ignition timing, the engine control module uses this input together with several others related to vehicle operating conditions. Except for the initial setting, ignition timing is decided by the engine control module.


TOP DEAD CENTER (TDC) SENSOR




The TDC sensor senses the top dead center on compression stroke of the No.1 and No.4 cylinders, converts it into a pulse signal and inputs it to the ECU. The ECU which then computes the fuel injection sequence, etc. based on the input signal.

Troubleshooting Hints
If the TDC sensor does not operate correctly, correct sequential injection is not made so that the engine may stall or run irregularly at idle or fail to accelerate normally.