What is a distributor and where is it located?

Before automotive manufacturers used individual coils per cylinder, the distributor was an important part of the ignition system. The distributor would tell the ignition coil at what moment when to fire and transfer the energy from the coil to a specific engine cylinder in order for engine ignition to occur. Older classic vehicles used breaker points and a condenser for this process (mechanical ignition system), whereas later models used electronic systems that relied on an ignition module and the engine’s computer for more precise timing (electronic ignition system). In modern automobiles, the distributor is no longer necessary as they are equipped with a distributorless ignition system, also referred to as a direct ignition system (DIS). In vehicles that do use a distributor assembly, it is located on top of the engine, either in front or in back of it depending upon the car or truck.

So how does an automobile distributor work, exactly? Basically, electricity from the battery is transferred to the ignition coil. The distributor then takes the high voltage output from the ignition coil and feeds it through the ignition wires to the spark plugs that are inserted into each engine cylinder in the order of the firing sequence. The distributor uses the rotation of the engine’s camshaft, which it connects to via the distributor shaft to spin the distributor rotor, which connects directly to the ignition coil, close to (but not touching) the individual cylinder points (or posts) underneath the distributor cap. Each of the points are connected via a spark plug wire—which connect to the top of the distributor cap via plug terminals—to the spark plug(s) screwed into each engine cylinder, and are arranged along with the wires according to the engine cylinders' correct firing order sequence. As the rotor spins within the distributor, electrical current is able to jump the gaps between the rotor arm and the individual contact points due to the high voltage created by the ignition coil. The electrical current is then transferred from the rotor to the spark plug wire, and then to each spark plug attached to each engine cylinder according to the firing order, allowing for proper ignition spark at just the right time for the engine to start.

Want to learn more about distributors and ignition systems? Then check out our in-depth article on distributor ignition systems.

When is a distributor replacement needed?

There are many components in an automotive distributor assembly, such as a coil, cap, rotor, pickup, ignition module, bearings, etc., and any of these parts are subject to wear and tear. Because of this, there are a variety of reasons why a distributor may need to be replaced. For models that have built in ignition modules, it can be more cost and time effective to replace the entire distributor assembly than to diagnose and replace just the electronic components. Worn bearings in the distributor shaft can cause erratic timing issues or ignition misfires. Bad internal seals can allow oil or moisture to get inside the housing and cause damage to vital components. These are but a few reasons for car distributor failure.

If your car or truck uses an ignition system that depends on an ignition distributor and it has failed, your engine will not be able to function properly, or at all, and thus your car won’t start when you turn the ignition key. Therefore, obtaining an ignition distributor replacement and getting it installed is imperative if you plan on driving your vehicle ever again.

Can I replace a distributor myself?

Replacing an auto distributor does require some intermediate understanding of the ignition and electrical system, but can be done by a do-it-yourselfer. A timing light, firing order, and top dead center are all terms that should be well understood before removing the distributor. Incorrect installation can cause permanent engine damage, so a repair or service manual is a very important tool to assure a properly executed fix. The steps can vary depending on the model, but some steps may require the removal of the air intake system. When you reach the distributer it's important to note which cylinders are which. Unplug each of the wires while being aware of their placement. Then remove the distributer cap and rotor, which might be held in place with a screw. When reinstalling, attach the cap and rotor and connect the plugs into their right place.