Skip to Content

How Does a Spark Plug Work? What Does It Do?

A car's spark plug against a dark background.

A spark plug is a device that helps create or ignite a spark to start a fire. It is usually made of metal and has an electrically charged tip. When the current from the charging device flows through the end, it causes a spark that can then be used to start a fire.

How does a spark plug start?

The spark plug is usually placed in the cylinder head of an engine, and its function is to create a spark that will ignite the air/fuel mixture in the engine’s cylinders. The spark plug consists of two electrodes, one of which is connected to the ignition system, and the other is connected to the ground.

When the ignition system creates a spark, it jumps across the gap between the two electrodes and ignites the air/fuel mixture in the cylinders. This process starts the engine.

How does a spark plug know how to fire?

3D depiction of a spark plug on a black backdrop.

High voltages in the ignition system are used to create a spark at the spark plug. These voltages can be generated in several ways, but the most common method is using a coil wrapped around an iron core. When the current flowing through the coil is interrupted, it creates a magnetic field around the iron core.

See also  Do EVs Have Radiators?

This sudden change in magnetic flux induces a high voltage across the coil’s terminals, which then jumps across the spark plug’s gap and creates a spark.

How does a spark plug create a spark?

The spark plug has two electrodes, one of which is connected to the ignition system, and the other is connected to the ground. When the current from the ignition system flows through the gap between the electrodes, it creates a spark. This spark ignites the air/fuel mixture in the engine’s cylinders and starts the engine.

What are some common problems with spark plugs?

Spark plug replacement work, with the mechanic's hand holding the old spark plug and a background of a car with a blurred engine.

One common problem with spark plugs is fouling. Fouling occurs when deposits build up on the electrode, which can eventually prevent the spark plug from firing. Another common problem is misfiring, which happens when the spark plug fails to fire or ignite the air/fuel mixture in the cylinder. This can cause the engine to run rough or stall.

How does a spark plug get electricity?

The high voltage lights the spark plug. It uses an induction coil wrapped around an iron core. The coil works as a transformer. The voltage is transformed from 12 to 15,000 volts. That’s enough to make the spark.

The primary coil has many turns of thin wire. The secondary coil has fewer turns of thicker wire. When the current flowing through the primary coil is interrupted, it creates a magnetic field around the iron core. This makes a voltage in the coil that jumps the spark plug’s gap. The electricity comes from the battery or an alternator. It goes through the ignition switch, coil, distributor, and then to the spark plugs.

See also  Do EVs Have Axles

The electricity comes first from the battery. Next, the power flows through the ignition switch and onto the coil’s primary winding. This makes a magnetic field in the iron core.

When it’s time for the spark, the current is interrupted. This sudden change in magnetic flux induces a high voltage across the coil’s terminals. The voltage jumps across the spark plug’s gap and lights the mixture in the engine’s cylinders. Then your engine starts!

How do spark plugs work without a battery?

Spark plugs being changed by an auto repair.

If the ignition system is designed properly, spark plugs can work without a battery. In this case, the ignition system would use a capacitor instead of a coil to store energy and create the spark. When the capacitor is discharged, it makes a high voltage that jumps across the spark plug’s gap and ignites the air/fuel mixture.

Types of spark plugs that generate electricity without a battery

Several types of spark plugs can generate electricity without a battery, such as those used in glow plug engines and magneto ignition systems. Glow plug engines use a small heating element in the spark plug that is powered by the engine’s compression to heat the air/fuel mixture and help start the engine.

Magneto ignition systems use a magnet to create a high voltage that jumps across the spark plug’s gap and ignites the air/fuel mixture.

How do I know if my spark plugs need to be replaced?

One way to tell if your spark plugs need to be replaced is by looking at them. For example, if the electrodes are worn down, or there is heavy carbon buildup, they will need to be replaced. Another way to tell if your spark plugs need to be replaced is by how the engine runs. If the motor is misfiring or running rough, it indicates that the spark plugs must be replaced.

See also  How Do Airless Car Tires Work? How are they Made? Benefits? Cost?

Related: How Often Should you Replace a Spark Plug in Vehicles?Are Spark Plugs Universal? Interchangeable?