Spark Plugs

Spark plugs create the current that ignites your fuel-air mixture.  Without them, nothing would happen when you turn the engine on and you would be marooned.

In each cylinder head of your petrol engine, electrodes in your spark plugs connect to the ignition coil/distributor through an ignition cable, creating a spark of at least 20,000 volts.

Glow plugs are the equivalent car parts for diesel engines.  While diesel combusts with hot, high-pressure air, petrol combusts with a spark.

Spark plugs should be replaced at every service.  Different engines require different types and quantities.  To identify the necessary replacements for your vehicle, enter your car details into our car part finder.

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

• Acceleration is poor.
• Spark plug surfaces are worn.
• The insulator is cracked.
• Engine start is hindered.
• Your engine vibrates during driving, even more so at idle.
• Your vehicle’s power capacity is reduced.
• Your fuel consumption has increased.
• There is increased carbon monoxide in your exhaust gas.

Why do my spark plugs need to be replaced?

• There is soot on the spark plug electrodes.
• The piston rings are worn.
• Your cooling system water pump is damaged.
• An incorrect operating temperature has been selected for your spark plugs.

How do I replace my spark plugs?

Spark plugs can’t be repaired, but they can be replaced without any technical expertise. 

Locate your spark plugs under the bonnet; they may be concealed beneath an engine cover.   Wait until the engine is cold and disconnect each ignition wire.  Use a ratchet to remove the spark plugs.  Lubricate your replacements and connect them to the ignition wires using the ratchet, referring to your car owner maintenance manual to check your required spark gap.

Spark plug brands stocked by DIY Car Service Parts