[Infographic] A Quick Guide to Spark Plugs

Have you ever wondered what makes a vehicle’s engine start? As professionals with auto mechanic certification know, spark plugs are among the most important parts involved in the process.

Spark plugs provide the spark or electricity that begins the entire combustion process. Individuals who are interested in careers in the auto industry may already know that the combustion process is what powers the vehicle’s pistons. Combustion gets the car’s pistons to move, which in turn allows the vehicle to drive. Without properly functioning spark plugs, that whole process may lose efficiency or even halt completely.

Want to know a little more about how spark plugs work? Check out our infographic below to learn more!


A Quick Guide to Spark Plugs

What is a Spark Plug?

  • An essential component of a vehicle’s combustion system
  • An electric piece that is located in the engine’s cylinder head
  • Spark plugs are made up of a shell, insulator, and conductor

The first spark plug ever made was crafted in 1860

How do Spark Plugs Work?

  • Spark plugs start the ignition process of a vehicle
  • A coil delivers high voltages of electricity to the spark plugs
  • The spark plug transfers the spark of electricity across a gap in the engine
  • The spark ignites the compressed oxygen and fuel in the engine
  • This begins the combustion process and starts the vehicle

Spark plugs typically need about 15,000 to 25,000 volts of electricity to start a car

Signs That Spark Plugs Need to be Replaced!

When spark plugs start breaking, it’s referred to as “misfire.”

5 signs that a vehicle is misfiring:

  1. The vehicle is making unusual rattling or knocking noises
  2. The vehicle is having trouble starting
  3. If the vehicle does start, it feels jerky and rough
  4. Reduced power and acceleration while driving
  5. Poor gas mileage

Did you know? When spark plugs misfire, fuel economy can lessen by 30%

What Can Spark Plugs Tell You About a Vehicle?

The best way to know if spark plugs need to be replaced is to remove and inspect them. The way they look can reveal clues about what’s going on under the hood. Here are some examples of common spark plug conditions:

Condition: Normal
Appearance: May have some dirt and grime
What it means: The spark plug is in good condition

Condition: Carbon-fueled plug
Appearance: Black, dry, and covered in soot
What it means: The air filter needs to be cleaned, the car has been idling for too long, or the car has been used for constant driving at low speeds

Condition: Oil-fouled plug
Appearance: Black, oily appearance, slick
What it means: Oil is leaking, possibly from damaged auto parts such as the pistons and valves

Condition: Burned plug
Appearance: Burned, blistered, and melted parts
What it means: Spark plugs aren’t firing at correct intervals, the engine is too hot, or the spark plugs may be loosening

Condition: Worn plug
Appearance: Electrodes are damaged and eroding away
What it means: The plug is too old

Some Benefits of Installing Brand New Spark Plugs:

  • Combustion process functions optimally
  • Improved vehicle performance
  • Improved fuel economy
  • Proactively replacing plugs can reduce future maintenance costs
  • Vehicle engine starts smoother and easier
  • Reduced harmful emissions

Did you know? Most manufacturers recommend replacing spark plugs every 30,000 miles







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