Distributor Parts Names, Functions, & Common Problems

The ignition distributor is an integral part of your car’s ignition system that helps in providing the power needed to start your car. Just like every other car component, different parts make it up.

While it has a single name, it comprises several components to help carry out its job judiciously. So in this article, I will walk you through your car’s distributor parts names and functions. But first, let’s see what an ignition distributor is.

What is an ignition distributor of a car?

An ignition distributor is an ignition system component that transfers electricity from the plug wires to individual spark plugs in the correct firing order. You should find it on the ignition system of cars with older engines.

distributor parts diagram
Distributor parts diagram

Distributor parts names and short description

The following are major car distributor parts and functions.

Distributor cap

The distributor cap serves as a protective covering for the internal components of the distributor. It also helps supply high voltage from the distributor to the ignition cables, which invariably fire up the spark plugs.


The distributor rotor is placed at the top of the distributor shaft and has the same rotating speed as the camshaft. It rotates together with the distributor shaft and helps fire each spark plug after reaching each outer terminal of the distributor cap.

Distributor shaft

Your car’s distributor shaft is found at the center of the ignition distributor and connects directly to the engine’s camshaft via a gear drive. It houses a cam used to break the contact breaker point.

distributor pick up coil

The pickup coil resides inside the distributor and typically helps trigger the ignition system to spark up.

Distributor wire

The distributor wires connect directly to the spark plugs and help transmit electricity to each spark plug.

Working principle of ignition distributor

The high current generated by the ignition coil is transferred to the distributor’s cap through the coil wire. The distributor cap, in turn, transmits this voltage to the distributor rotor. Since the rotor is connected to the distributor shaft, it rotates as the shaft rotates.

As the distributor rotor rotates, it transmits current to the outer terminals of every distributor cap. From the cap’s outer terminals, the current travels to individual spark plug via the spark plug cables. This ultimately sparks the spark plug to ignite the fuel-air mixture in the combustion chamber.

Ignition distributor common problems and fixing

The following are common ignition distributor problems and how to fix them, with the distributor cap and rotor as the most common.

Common problems

Here you go with the frequent issues; you will encounter and need to fix, with different distributor parts.

Cracked or broken distributor cap

One of the most common problems an ignition distributor faces is the distributor cap getting broken or cracked. Typically, a faulty distributor cap comes with loads of problems which will be evident in the way your engine performs.

First, a faulty distributor cap will cause your engine to start misfiring. Generally, aside from protecting the distributor’s internal components, the distributor cap helps regulate the engine’s firing sequence. So when the distributor cap is faulty, it won’t supply sufficient spark to the spark plugs, invariably leading to engine misfires.

A failing distributor cap will also cause your entire car to shake since it will fail to supply current in the correct cylinder stroke. Again, because a faulty distributor cap won’t transfer enough current to the spark plugs, proper combustion won’t occur. Invariably leading to loss of power, eventually causing your car to stall and backfire. So for those asking, can a bad distributor cause loss of power? Now you know.

Improper combustion will also cause the check engine light to come on. Usually, once the ECU detects disorderliness in the firing sequence of the spark plugs, it turns on the CEL. In other cases, the car won’t start at all since enough power needed for combustion isn’t supplied to the spark plugs.

Cars not starting at all are particularly noticeable during the cold months. Here, because the cap and other distributor parts freeze during the cold months, the heat that emerges during start-up time causes the cap and other parts, like the shaft and rotor, to break.

To fix engine misfiring, CEL, and other problems highlighted here, replace the distributor cap and rotor. You may also need to stop leaving your car out in the cold or in an unheated garage with low temperatures to prevent the cracking of distributor parts during start-up.

Failing rotor

Another common problem of a distributor is a failing rotor. And just like a failing distributor cap, a bad rotor comes with many problems. With car shaking and improper combustion as the most noticeable symptoms of bad distributor rotor.

Generally, the rotor spins and is responsible for firing individual spark plugs. If the rotor cannot spin as it should, it will cause your car to start shaking. Sometimes it starts from a light vibration to a more serious one, which is felt throughout the car.

A cracked cap or clogged distributor cap can also cause the rotor not to spin properly, invariably preventing the engine from reaching optimal combustion. A broken rotor caused by heat surge during the cold months will also not allow your car to start at all. A clogged distributor rotor will cause the check engine light to turn on due to improper combustion.

To fix, check if the rotor is spinning correctly; also, check for cracks on the distribution cap. Typically, the distributor cap and rotor work in synergy.  Note that the check engine light would turn on for other reasons. So if the lights refuse to turn off after replacing the cap and rotor, you may need to do a further inspection to find the real culprit.

Failing distributor shaft

Like other faulty distributor parts, a failing shaft comes with loads of problems. With the most noticeable symptom of a bad distributor shaft being hard starting or the car not starting. The rotor practically sits on the shaft. So if the shaft is bad and can’t rotate, the rotor won’t as well.

If the rotor can’t rotate, the spark plugs won’t get the current to fire up. If the spark plugs can’t fire, there won’t be combustion. Improper combustion will lead to hard starting or the car not starting, and even if it starts, it may stall, shake aggressively, or even misfire.

Clogged distributor cap

Clogging is another issue common with a distributor. A carbon-fouled distributor cap will cause hard starting. In some cases, when the distributor cap is clogged, you will hear a squealing noise, when starting the engine. What happens is that a clogged distributor cap blocks the circulation of air, invariably producing an intense or high-pitched sound.

To fix this, check under the distributor cap and do a thorough clean-up. Ensure you clean all the carbon deposits inside the cap. Pay more attention to the contact points. If the hard starting continues after this, take your car to an expert for a thorough inspection. And if you are wondering, what does a bad distributor sound like? Now you know.

Crankshaft and timing belt issue

While the crankshaft isn’t a distributor component, it can cause issues making it look like it’s the distributor’s fault. The movement of the crankshaft is what is called a turnover. Hence, a faulty crank will cause your vehicle to have difficulty turning over, along with stalling. Even a bad timing belt can cause this.

To fix the issue, check the distributor cap and ensure it is not loose. If it is, retighten it. If this doesn’t solve the problem, it could be a loose crankshaft or timing belt issue. A loose cap will prevent the distributor from sending enough power to the spark plug to initiate combustion.

Damaged distributor wire

The distributor wires can get damaged for several reasons, causing an inconsistent supply of electricity to the plugs, invariably leading to irregular RPMs. Check to see if the wires are damaged and get them replaced.

If this doesn’t fix RPM issues, it may be that the distributor cap and rotor are cracked, broken, or carbon-fouled. Also, check if the rotor is turning as it should.

Distributor pick-up coil issues.

The pickup coil resides inside the distributor and typically helps trigger the ignition system to spark up. A faulty pick-up coil won’t provide the spark for the spark plugs, so your car may experience difficulty starting or won’t at all.


Common distributor problems highlighted are associated with certain symptoms which have been discussed above. When you see those faulty distributor symptoms, address the issues immediately by diagnosing the distributor. The diagnosis allows you to check all distributor components to fish out the actual culprit.

To do this, you will need a racket, flashlight, spark plug, magnetic screwdriver, voltmeter, etc. Now, here is how to test a distributor. The two most common distributor problems are the distributor cap and rotor. So take off the cap with the racket and socket and check the cap for cracks, corrosion, burns, or dirt.

Then move onto the rotors. Replace cracked cap and rotor; clean up carbon-fouled, dirty, or rusty cap and rotor. Pay more attention to the contact points and clean them properly.

After this, check the spark plug wires and move to other distributor parts. If all distributor components seem ok, yet you’re having issues starting your car, you may need to check other components of your car’s ignition system.

Final Words

Knowing distributor parts names and functions is an easy way to spot an issue with the distributor when there is one. This way, you can quickly fix the issue before it escalates and damages other connected components.

While the most common distributor problems produce specific symptoms, understand that those symptoms could also arise due to other faulty car components. Hence, the need to carry out a distributor test. This test not only helps you verify if the distributor has an issue but also tells which distributor components are causing the issues.



While growing up, I knew I had a thing for car repairs though my parents never wanted me to learn mechanics. I always visit a mechanic garage in my small neighborhood after school. As I grew older, at age 16, I got addicted to anything automotive. My parents had to enroll me in that mechanic garage since giving up was never an option for me. As a dedicated mechanic who got into the industry from an early age, I'm graced with an addiction to diagnosing and rectifying automotive problems with ease.

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