The distributor ignition system differs from the conventional breaker points system in form only; its function is exactly the same: to supply a spark to the spark plugs at precisely the right moment to ignite the compressed air/fuel mixture in the cylinders and create mechanical movement.
Located in the distributor, in addition to the rotor, is a spoked reluctor which is pressed onto the distributor shaft. The reluctor revolves with the rotor; as it passes a pickup coil inside the distributor body, it breaks a high flux field, which occurs in the space between the reluctor and the pickup coil. The breaking of the field allows current to flow to the pickup coil. Primary ignition current is then cut off by the Powertrain Control Module (PCM), allowing the magnetic field in the ignition coil to collapse, creating the spark which the distributor passes on to the spark plugs.
The distributor ignition system has timing controlled by the Powertrain Control Module (PCM). The standard reference ignition timing data for the engine operating conditions are programmed in the memory of the PCM. The engine conditions (rpm, load and temperature) are detected by various sensors. Based on these sensor signals and the ignition timing data, a signal is sent to interrupt the primary current at the power transistor. The ignition coil is activated and a spark sent through the distributor, down the spark plug wires to the spark plugs. Ignition timing is controlled by the PCM for optimum performance.
The distributor ignition system can be identified by looking for the presence of a distributor (with spark plug wires connecting the distributor cap to the spark plugs). If no distributor is found, it can be assumed that the engine uses a distributorless ignition system. Coverage of the distributorless ignition system is found later in this section.