How Does the Spark Plug Work?

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If you must know, the first Spark Plug was invented in 1903 by Oliver Lodge. Spark Plugs are used in petrol engines. Diesel engines use a different type of component called a glow plug which reduces cold start issues.

Diesel engines compress the air then inject diesel fuel into the heated and compressed air mixture where it auto ignites.

Spark Plugs transmit electrical signals from the ignition coil creating a durable electrical spark that ignites the air-fuel mixture. Though seemingly tiny and simple, spark plugs are tasked with quite a significant role in a petrol engine.

How Does the Spark Plug Work?

The spark plug is an electric device that sits at the upper part of the cylinder head. It has an insulated center electrode that is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside. It forms a spark gap together with the grounded terminal on the base of the spark plug.

It transmits very high electrical energy/voltage in order to create a spark that ignites gasoline and air mixture in the combustion chamber. This is how it works:

 A mixture of air and gasoline is drawn into the combustion chamber by the piston moving down inside the cylinder.

 The air and petrol mixture is compressed in the combustion chamber by the piston moving up inside the cylinder towards the spark plug.

 When the piston is at its fullest, the fuel and air mixture is ignited by the spark plug in the combustion chamber. A powerful electric charge generated by an ignition coil or magneto is transmitted through the spark plug skipping the gap in the plug and firing up the end.

This spark ignites this mixture. This causes an explosion inside the burning chamber. The force of the explosion pushes the piston to move back down inside the cylinder creating power for the vehicle.

 The spent gasses from the explosion (exhaust) are then forced out of the burning chamber by the piston that is pushed back up again.

A four-cylinder car has four spark plugs. Similarly, a six-cylynder motor vehicle has six spark plugs. However, this does not apply to all engines. A HEMI engine has two spark plugs per cylinder. Check out our next post on Signs of a Faulty Spark Plug.