Spark Plug Visual Inspection

^ Normal operation-Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with additives.
^ Carbon Fouled-Dry, fluffy black carbon, or soot caused by the following conditions:
- Rich fuel mixtures
^ Leaking fuel injectors
^ Excessive fuel pressure
^ Restricted air filter element
^ Incorrect combustion
- Reduced ignition system voltage output
^ Weak coils
^ Worn ignition wires
^ Incorrect spark plug gap
- Excessive idling or slow speeds during light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off.
^ Deposit Fouling-Oil, coolant, or additives that include substances such as silicone, or very white coating, reduce the spark intensity. Most powdery deposits will not affect the spark intensity unless the substances form into a glazing over the electrode.