The Distributor Ignition (DI) system consists of the following components:
The primary (low voltage) ignition circuit includes the ignition switch, power transistor, and ignition coil primary winding. The secondary (high voltage) circuit consists of the ignition coil secondary winding, coil wire, distributor cap and rotor, spark plug wires, and spark plugs.
The camshaft position sensor (CMP), located inside of the distributor, sends engine speed and piston position signals to the Powertrain Control Module (PCM). The PCM then sends electrical pulses to the power transistor, which switches the ignition coil primary circuit on and off. This switching induces high voltage in the coil secondary circuit, which is applied through the distributor cap, rotor, and plug wires, firing the spark plugs. A feedback circuit from the primary ignition circuit sends an ignition reference signal through the resistor back to the PCM. Ignition timing advance and retard functions are controlled by the PCM, which receives signals from various switches and sensors to determine when to send pulses to the power transistor.