The ignition distributor, sometimes simply called the distributor cap, has the responsibility of relaying high-voltage electricity to each individual ignition wire. Each wire then carries the current to a spark plug that emits the electrical charge as a spark in its engine cylinder. The timing of the sparks delivered to each cylinder is important if your car is to operate efficiently and within its full potential. Knowing how the distributor actually works can give you a greater appreciation for the decades-old engineering marvel that keeps millions of cars on the road.
The ignition distributor is actually a very simple device. There are two types that may be found in most cars on the road today, but the one currently installed in almost all new cars worldwide uses a separate cap and rotor assembly that is simpler than the earlier model. First, an electronic coil sends a high-voltage electrical current to the rotor within the cap. The rotor spins past a series of contacts, each one leading to a different cylinder of the engine. As the rotor spins it releases an arc of electricity to each contact and that current is carried to individual ignition wires that will deliver the charge to the spark plugs. The rate of spin of the rotor depends upon the engine speed required.
When performing a tune-up on your car, it is important to check the rotor and cap for wear. Just as the spark plugs eventually wear due to the high-voltage sparking they do for many years, so can the distributor. There is no way to easily repair a damaged or worn distributor, so replacement is the only option. When planning for a tune-up, take into consideration the cost of a new ignition distributor.
Modern cars do not have “breaker points” within their distributor that controls the electrical current discharged, but older cars may still have this type of distributor. If you have an older car with the former style of distributor, it may be necessary when doing a tune-up to check the setting of the points. This can be difficult unless you understand completely how this is done, so asking a mechanic to check these during a tune-up would be best. The older model of distributor is more intricate than the more modern model and contains several more parts, such as an individual condenser, and may in some cases be expensive to replace. Newer models of cars in some cases may not have a distributor at all and are referred to as “distributorless”.