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Spark Plugs
Spark plug condition is indicative of engine operation. The spark plug
firing end condition should be read after the engine has been warmed up
and the vehicle has been driven at higher speeds. Immediately check the
spark plug for correct color.
CAUTION! A hot exhaust system and engine can cause burns. Wear
protective gloves when removing a spark plug for inspection.
Normal Spark Plug
The normal insulator tip is gray, tan or light brown. There will be few
combustion deposits. The electrodes are not burned or eroded. This indi-
cates the proper type and heat range for the engine and the service.
The tip should not be white. A white insulator tip indicates overheating,
caused by use of an improper spark plug or incorrect carburetor/throttle
body adjustments.
Wet Fouled Spark Plug
The wet fouled insulator tip is black. A damp oil film covers the firing
end. There may be a carbon layer over the entire nose. Generally, the
electrodes are not worn. General causes of fouling are excessive oil, use
of non-recommended injection oil, improper use of the choke, or incor-
rect carburetor/throttle body adjustments.