Distributor: Description and Operation

Electronic Spark Control Ignition System:

Distributor Exploded View:

The basic components of this ignition system are the ignition coil, the distributor, the spark plugs, and the spark plug wiring. The distributor consists of a signal generator (signal rotor and pickup coil) and ignitor.

When the distributor shaft rotates, a fluctuating magnetic field is generated due to changes in the air gap between the pickup coil and the signal rotor. As a result, an alternating current (AC) voltage is induced in the pickup coil. The induced AC voltage peaks when a ridge on the signal rotor is adjacent to the ridge on the pickup coil. When the voltage peaks, the ignitor breaks the circuit to ground from the negative (-) side of the primary winding. With the circuit broken, the magnetic field in the external ignition coil, which was generated by an electrical current passing through it, collapses. The high voltage induced by the collapsing field is then forced to find a ground through the secondary coil wire, the distributor cap, the rotor, the spark plug wires, and finally across the spark plug gap to the engine block.

All spark timing changes in the distributor are performed electronically by the ECM. The ECM monitors information from various engine sensors, computes the desired spark timing and signals the distributor to change the timing accordingly. No vacuum or mechanical advance mechanisms are used on this system.