Banshee Spark Plugs - What are they telling you?

February 6, 2025

Paying attention to the condition and appearance of your Banshee's spark plugs can tell you a lot about how your engine is running. This can help you maintain optimal engine performance and prevent costly damage.

Analyzing the color of the insulator's firing nose can give experienced engine tuners important clues about how the engine is doing overall.

Usually, a light tan/gray color means the spark plug is operating at optimum temperature and that the engine is in good condition.
Dark coloring, such as heavy black deposits, whether wet or dry, may indicate an overly rich condition, a heat range that is too cold for the spark plug, a possible vacuum leak, low compression, overly retarded timing, or a plug gap that's too large.
If the deposits are wet, it could mean your engine has different problems. These might include a breached head gasket, poor oil control from ring, or an extremely rich condition. This depends on the nature of the liquid present at the firing tip.
Signs of fouling or excessive heat must be addressed quickly to prevent further deterioration in performance and potential engine damage.

An engine’s condition can be judged by the appearance of the spark plug’s firing end. The following is a list of spark plug conditions with a picture showing what each looks like. Hopefully this will offer some clues to show you how your Banshee is operating.

	Normal Condition If the firing end of a spark plug is brown or light gray, the condition is good and the spark plug is functioning optimally.
	Overheating When a spark plug overheats, deposits that have accumulated on the insulator tip melt and give the insulator tip a glazed or glossy appearance.
	Dry and Wet Fouling The optimal operating rage for ohms is 0-10 ohms. If the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon.
	Deposits The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality, and the duration of engine’s operation.
	Lead Fouling Lead fouling usually appears as yellowish brown deposits on the insulator nose. This cannot be detected by a resistance tester at room temperature. Lead compounds combine at different temperatures. Those formed at 370-470°C (700-790°F) have the greatest influence on lead resistance.
	Abnormal Erosion Abnormal electrode erosion is caused by the effects of corrosion, oxidation and reaction with lead—all resulting in a gap that is too large.
	Normal Life A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages.
	Erosion, Corrosion and Oxidation When the material of the electrodes has oxidized and the oxidation is heavy, it will be green on the surface. The surface of the electrodes is also fretted and rough.
	Lead Erosion Lead erosion is caused by lead compounds in the gasoline which react chemically with the material of the electrodes (nickel alloy) at high temperatures; crystals of nickel alloy fall off because of the lead compounds permeating and separating the grain boundary of the nickel alloy. Typical lead erosion causes the surface of the ground electrode to become thinner, and the tip of the electrode looks as if it has been chipped.
	Breakage Breakage is usually caused by thermal expansion and thermal shock due to sudden heating or cooling.