An important component of the ignition system, spark plugs provide electrical current to the combustion chamber in a petrol engine. The spark produced ignites the engine enabling the air/fuel mix to burn in the cylinders and combustion to occur.

Spark plugs are an insulated plug, made up of a copper electrode, surrounded by either nickel alloy, platinum or iridium and covered with a ceramic casing. The spark plug is fixed to the cylinder head in the engine to provide the spark required to ignite the air and fuel that flows into the engine. There will be a spark plug for every cylinder of the engine. 

In this type of ignition system, the high voltage electrical pulses which are needed to supply energy to the spark plugs are provided by a magneto. A magneto is made up of a magnet which spins around inside a coiled wire, positioned in the inner rim of the flywheel, which is connected to the electrode inside the spark plug by a spark plug wire. The magneto generates its own magnetic field of energy which is used to power the spark plugs in order for combustion to occur. Spark plugs also function to take heat away from the combustion chamber by transferring the heat produced in the engine to the cooling system. The materials used in the spark plug help to transfer the heat away from the combustion chamber to outside of the engine. Spark plugs can be either hot plugs or cold plugs. Hot plugs are insulated more than cold plugs which helps to maintain a high temperature within the spark plug which burns off carbon deposits meaning the engine components ultimately work better and last longer. The advantages of cold plugs being less insulated, is that this allows for greater dispersion of heat away from the combustion chamber, and these are generally used in high compression super-charged engines. 

It is important to ensure the spark plugs on your vehicle are in excellent condition and working well. Signs that the spark plugs may need changing on your car are an engine that struggles to start or will not start at all. It is always a good idea to consult with your mechanic when engine problems strike, to make sure the correct fault has been identified. When you need to change the spark plugs, a good quality set of spark plugs will guarantee a part that fits well, performs properly and has a long service life.