Spark Plug Repair - Get an online auto repair estimate

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Spark plugs are installed in the engine cylinder head and located with the spark plug electrodes or tip within the combustion chamber. Engines may have one or two spark plugs per cylinder and each spark plug can have from one to four electrodes. When an appropriately-timed electric spark occurs at the spark plug electrode, ignition occurs within the combustion chamber. Spark plug types are specific to each vehicle and should be replaced according to the manufacturer's specifications.

Mechanics' Corner: More Technical Detail

The spark plug is a metal and ceramic device that is threaded directly into each cylinder's combustion chamber. There are two electrodes on each spark plug. The center electrode is connected to the spark plug wire that runs from the cap of the distributor. This center electrode is insulated by ceramic material from the ground electrode. The ground electrode is on the outer edge of the spark plug and is part of the threads that screw directly into the cylinder head. There is a gap between the center and ground electrode (usually about the width of a penny) that the high voltage jumps across, which creates an arc of electricity similar to a lighting bolt. This ignites the compressed mixture of air and fuel inside the combustion chamber that pushes down on the piston as it burns and expands.