Distributors 101

March 20, 2025

6 min read

March 20, 2025

6 min read

If your vehicle has a distributor, you can easily spot it in your engine bay. Trace the spark plug wires back from the engine to find them converging at a little cylinder sticking out of the engine. That’s the distributor. If you are experiencing engine trouble, the distributor might be at fault.

They’re generally robust, but they can go bad. When they fail, you probably have an easy repair ahead. Probably.

What a Distributor Does

A distributor with a black cap sits between a high-performance V-8 engine and the firewall. — The distributor on this high-performance V-8 sits between the engine and the firewall.

Distributors are the main ignition component in cars that do not have computer-controlled ignitions. If your car was built before the mid-2000s, there is a good chance it uses a distributor. If it was built after the mid-1970s, the distributor likely uses an electronic control module to supply spark. If it was built before the mid-1970s, chances are it uses a set of contacts called points to generate a spark.

The distributor’s job is to distributepower to each spark plug in a specific order. They’re timed with the rotating assembly of the engine to send a spark to each cylinder in a set sequence. Inside the distributor is a rotor. It generates a spark via an electric contact in the cap that corresponds to each cylinder. The power arcs across a diode on the end of the spark plug inside the cylinder, igniting the fuel mixture.

The spark plug wires on the cap must follow the engine firing order. If they don’t, the engine can’t run properly.

How long does a distributor last?

Assuming you drive your car regularly and keep up with maintenance, a distributor should last many years and more than 100,000 miles. However, the distributor cap and rotor should be considered consumable parts and must be replaced every few years.

This works in your favor. The items inside the distributor that more frequently wear out are easy to replace. The distributor as a whole unit is difficult to replace but rarely wears out.

The signs of a bad distributor are common to a bunch of engine problems, so figuring out if your distributor is bad can be tricky. Fortunately, you can test a distributor pretty easily.

A bad distributor can cause a vehicle to misfire, stall, or not start at all. Faulty distributors can also make the car feel low on power, get poor fuel economy, or surge and hesitate at cruising speed. The tricky part is that poor fuel delivery, a bad fuel mixture, bad spark plugs, bad spark plug wires, or a dead ignition coil can all cause similar symptoms. Check all of those components first, then move on to the distributor.

Replacing the Whole Distributor Is No Small Job

A mechanic wearing a black nitrile glove unfastens a distributor with a screwdriver. — Removing a distributor can be tricky, but it does not usually require expensive tools.

More often than not, the rotor, distributor cap, points, or igniter are bad and can be replaced without changing the entire distributor. Those fixes are all pretty cheap and simple.

If that doesn’t fix the issue, you have to replace the distributor itself. Unfortunately, replacing the distributor is a much trickier, time-consuming, and labor-intensive job. We wouldn’t recommend it to a novice.

If you want to replace the distributor yourself, eBay Motors has a thorough DIY guide and video - opens in new window or tab.. And as always, use the eBay Parts Finder - opens in new window or tab. to make sure you get the correct part for your vehicle.

You don’t need any special tools, but you need to take your time and not skip any steps. Distributors are sensitive to correct installation. It’s easy to mess the job up if you don’t follow the steps in order, especially if it’s your first time.

Here’s some good news: If your distributor is acting up, it’s likely the cap, rotor, points, or igniter. Those parts are usually replaceable and generally cheap. If you can follow the directions for setting up a TV stand, chances are good you can change your distributor cap and rotor.

Costs to Replace a Distributor

A mechanic fastens a new distributor to a V-8 engine with a specialized distributor clamp wrench. — You may need a distributor clamp wrench to complete the job. Thankfully, they are not expensive.

A good-quality OEM or equivalent distributor assembly likely costs at least $250 but could be double or triple that for an uncommon vehicle or a European car. Depending on the shop and diagnostic time, changing a distributor is usually a two- or three-hour job at roughly $100 to $125 an hour. That means having a professional do the work could easily come close to the $1,000 mark.

You can likely halve that by doing the work yourself, but having the job done right may be worth the spend. If you mess up installing that distributor, more expensive repairs to the rest of your engine may be waiting for you. If you are committed to learning how to do the job, see our guide and perhaps seek help from a knowledgeable friend.

Change These Parts When You Change Your Distributor

A mechanic wearing a blue nitrile glove checking the gap on a spark plug. — You will need to set the gap when installing spark plugs on an older vehicle.

To get the absolute best out of your new distributor, we recommend replacing the distributor cap, distributor rotor, spark plug wires, and spark plugs.

If you’re already paying to change your distributor, you’d be silly not to check the consumable parts that work in tandem with the distributor. A brand-new distributor is no good if you have worn-out spark plugs or shot plug wires. If, for some reason, the new distributor doesn’t come with a new cap and rotor, it’s folly to throw the old parts in with the new.

About the author

Aaron Richardson

Aaron learned early on that it's easier to be decent at a bunch of stuff than great at one thing, which led neatly to a career as a writer. He has been an automotive writer, a newspaper editor, and a business reporter, and has always worked on his own cars and bikes. When he isn't writing stories, he's wrenching on a '74 BMW 2002 or riding a motorcycle.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.