TROUBLESHOOTING
Examining the spark plugs that are removed from an engine can help you determine if the engine has problems that need to be corrected. Here’s what to look for.
NORMAL
1. Normal – Grayish-tan to white in color. No unusual signs of deterioration or coatings.
RED COATING
2. Red coating – Pinkish red coating on the ceramic insulator tip, center electrode and ground electrode. Sometimes spark plugs will have a slightly red coating, which is the normal result of additives used in some unleaded gasoline.
WORN OUT
3. Worn out – The center and ground electrodes are eroded, have rounded edges and are excessively worn away. Difficulty starting the engine and misfiring during acceleration may occur. This indicates a spark plug that has been used beyond its intended service life.
4. Fuel fouled – Firing tip may be damp with gasoline, and usually the odor of gasoline is present on the spark plug. The insulator is often tinted the color of charcoal. This indicates that gasoline is not being burned properly in this cylinder. Check for faulty or sticking choke, overly rich fuel mixture, ignition problems, leaking fuel injectors or a spark plug heat range that is too cold.
FUEL FOULED
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