Plug with carbon deposits bridging to the ground electrode
Carbon Deposits
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Bridging is when deposits accumulate between the center electrode and the outer shell or base of the ground electrode. These deposits can form a "bridge" for an improper spark path from the center electrode to the outer shell. As mentioned below, the accumulation of deposits on the firing end sufficient enough to cause bridging can be caused by oil leakage, fuel quality and the engine's operating duration. Depending on the application, there are a variety of self cleaning designs used by Autolite to reduce bridging.
Deposits can occur from a variety of sources such as fuel additives, oil from a leaky valve guide, carbon build up caused by weak ignition or sticky valve, etc. It may be none of the above and the motor just may not be reaching full operating temperature to clean the deposits off the plugs. Regardless of the cause, accumulation will eventually lead to fouling and possible bridging. |
