Kohler RDC2, Operation

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TP-7102 3/20 59 Section 4 Scheduled Maintenance
Problem/Condition Means of Identification Possible Cause/Solution
Gap-bridged spark
plug
Built-up deposits and gap between electrodes
closing.
Oil or carbon fouling. Clean and regap the spark
plug.
Oil-fouled spark plug Wet, black deposits on the insulator shell, bore,
and electrodes.
Excessive oil entering combustion chamber
through worn rings and pistons, excessive clear-
ance between valve guides and stems, or worn
or loose bearings. Replace the spark plug.
Carbon-fouled spark
plug
Black, dry, fluffy carbon deposits on insulator
tips, exposed shell surfaces and electrodes.
Incorrect spark plug, weak ignition, clogged air
intake, overrich fuel mixture, or excessive no-
load operation. Clean and regap the spark plug.
Lead-fouled spark plug Dark gray, black, yellow, or tan deposits; or a
glazed coating on the insulator tip.
Caused by highly leaded fuel. Replace the spark
plug.
Pre-ignition damaged
spark plug
Melted electrodes and possibly blistered insula-
tor. Metallic deposits on insulator suggest inter-
nal engine damage.
Wrong type of fuel, incorrect timing or advance,
too hot a plug, burned valves, or engine over-
heating. Replace the spark plug.
Overheated spark plug White or light gray insulator with small black or
gray/brown spots with bluish (burned) appear-
ance on electrodes.
Engine overheating, wrong type of fuel, loose
spark plugs, too hot a plug, low fuel pressure or
incorrect ignition timing. Replace the spark plug.
Worn spark plug Severely eroded or worn electrodes. Caused by normal wear and failure to replace
spark plug at prescribed interval. Replace the
spark plug.
Figure 4-10
Engine Evaluation Using Spark Plug Condition