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Air Gap- Three Ground Electrode Spark Plug

Bulletin 1018

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Vehicle applications using standard type triple ground electrode spark plugs


Multi-ground electrode spark plugs can be difficult to determine the correct gap measurement. The gap is preset during manufacturing and should not be adjusted. However, situations do arise which could make it necessary to check the gap setting. This bulletin focuses on standard type triple ground electrode spark plugs and the procedure required to measure the gap setting if needed.


All standard multi ground electrode spark plugs have a factory pre-gaped setting. This setting should not be altered in any way for any reason. If the gap setting of a spark plug with multi-ground electrodes comes into question, a wire style gap tool must be used to verify the pre-gap setting. This tool will allow the gap and or air gap to be checked safely without applying pressure to any of the electrodes or damage to the insulating ceramic. The image below illustrates the gap measurement. The air gap measurement is from the ground electrode to the ceramic insulator. Reference the engine application guide for specific gap specification.

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