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Molten center electrode or melted ground electrodes and center electrode. Possibly fractured and melted ceramic. Occasionally, melted steel shell. |
PRE-IGNITION DETONATION. A melted nickel center electrode and/or melted ground electrodes always indicate that the spark plug has encountered higher than normal operating temperatures. Since the melting temperature of nickel is 2600°F, melting nickel indicates that the spark plug has probably been a victim of sustained pre-ignition or detonation. Check engine timing, mixture controls, and all engine functions. |
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Red, grainy deposits on insulator nose and firing end. |
IRON OXIDE DEPOSITS. Firing end deposits of iron-oxide may prevent the discharge of energy across the spark gap. These iron oxide deposits usually indicate that there may be corrosion in the fuel gas line or the main transmission pipeline. If the engine has cylinder injection air starters, corrosion may also be found there. Lastly, iron oxide deposits may indicate a cracked cylinder head. |
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