What Are Spark Plugs And Why Are They Important?


July 31st, 2020

Every internal combustion engine has a set of spark plugs. Their purpose is to ignite the fuel mixture in the combustion chambers.

If you want to learn more about spark plugs, this is the post to read. We have all the answers to the most common questions car owners have about spark plugs. We also carry OEM replacement spark plugs for all makes and models. Our best sellers include:

What Is A Spark Plug And What Does It Do?

A spark plug is a small tube-shaped part that’s only a few inches long. There’s one spark plug for each combustion chamber in the engine.

Ford spark plug #CYFS-12F-5, for various 2018-2020 Ford models

Spark plugs may seem like small and simple parts, but they're what keeps your engine running. They provide the spark needed to ignite the fuel mixture within the engine. When the fuel mixture is ignited, it creates small explosions that power the engine. In other words, your engine can't run without spark plugs.

The Main Components Of A Spark Plug

Spark plugs contain many small, yet important, components that work together. Some of the main components include:

  1. Terminal: The terminal is a metal tip that connects to the ignition system via the coil or spark plug wires.
  2. Ceramic insulator: The insulator:
    1. Insulates the terminal, center shaft, and center electrode from the housing
    2. Prevents the high voltage from escaping
  3. Electrodes (center and side): Each spark plug comes with a center electrode and a side electrode.

How Does A Spark Plug Work?

Spark plug

A spark plug screws into the cylinder head. The electrodes are facing down, into the combustion chamber. Beneath the spark plug is a piston. The piston first draws in the air and fuel, and then it compresses the air/fuel mixture as it travels up toward the spark plug. While that happens, the spark plug ignites the air/fuel mixture.

The spark plug gets power from the ignition coil. The ignition coil converts the low voltage current from the battery into high voltage current. It then sends the high voltage current to the spark plug. The spark plug then creates a spark. This ignites the air/fuel mixture within the combustion chamber. An ignited air/fuel mixture creates a small explosion that drives the piston downward and powers the engine.

What Happens When A Spark Plug Fails?

For many engines, the rule of thumb is to replace your spark plugs every 100,000 miles. But some engines require new plugs much sooner, in as little as 30,000 miles. Sometimes spark plugs fail early. When that happens, you’ll know. You'll notice the following symptoms:

  • Poor fuel economy
  • Misfiring
  • Poor engine performance
  • Dirty exhaust
  • Rough idle
  • Difficulty starting the engine

When that happens, you need to replace the bad spark plug(s) in your engine. But it's best to replace the entire set at the same time. Luckily it's a pretty easy job. You can find a model-specific tutorial online.

Do you have any questions related to spark plugs? We'll be happy to answer them if you contact us!