How to Read a Spark Plug

Healthy spark plugs are integral to the performance of your engine. You'll receive better gas mileage and put less wear on the surrounding components of your engine. You should know how to read spark plugs to tell when they need replacing.

Instructions

1

Look for dry and wet fouling of the spark plugs. A spark plug should have a light grey or tan hue to it and must be dry to be in good working condition. Black carbon build-up or wet oil on the plug indicates a bad plug.

2

Check for overheating of the spark plug. If the spark plug has become too hot, the tip will look glazed. The spark plug is bad and you need to replace it. Also, check if the air-fuel mixture is too lean as a possible cause. You'll need to correct that to avoid the same issue in the future.

3

Inspect for off white or white deposits crusting around the spark plug head. Replace them immediately. Examine for oil leakage from the oil rings and valves and check for the wrong oil viscosity within the engine as a possible cause.

4

Think about lead deposits if you find brown and yellow spots on the head of your spark plugs. This usually means that the lead content is too high. Examine the gasoline you are putting in your engine.

5

Determine if the spark plugs have simply run their natural course. If the color is fine, but the gap between the tip and the plug has grown, then the spark plugs will be less efficient. It's time to replace the spark plugs.

6

See if the spark plugs have melted. If so, the tip of the plug will seemingly become one with the head of the unit. This is because temperatures that are too high within the combustion chamber. Change the spark plugs and correct the combustion chamber temperature.