Spark plugs are only found in petrol engines. Their purpose is to ignite the air/fuel mixture in the combustion chamber to start the engine. To ignite the mixture, the plugs let off a little spark which allows the air/fuel mixture to explode. For that spark, the plugs are powered by the HT leads.
Spark plugsare constantly subjected to rather extreme temperatures (varying from -50°C to plus 1000°C) and high voltage current up to 30 000V. All this causes your spark plugs to wear. They will therefore regularly need replacing; every 12 500 to 30 000 miles. Fortunately, spark plugs are not very expensive. Prices vary between £ 2.20 and £20. To determine which spark plugs you need for your Ford, please select the model and engine type of your car into the menu.