Ignition System - Kohler 15REYG Operation

3.7 Ignition System

Service the spark plugs at the interval specified in the
service schedule using the following procedure.
1. Remove spark plug wires by grasping the spark
plug boot and turning slightly while pulling. Do not
pull the wire. Pulling on the wire rather than the
boot may damage the wire or terminal.
2. Loosen the spark plug with a ratchet and 5/8-in.
spark plug socket with a rubber insert to prevent
spark plug damage.
3. Use compressed air to remove dirt from around
each spark plug to prevent dirt particles from falling
into the combustion chamber.
4. Remove spark plugs, one at a time, and examine.
Identify a normal spark plug in good operating
condition by observing a light tan or gray deposit on
the firing tip. See Figure 3-9 to evaluate engine
condition by color/condition of a problem spark
plug.
5. Clean spark plugs by wiping them with a rag. File
the center electrode to keep it parallel to the side
electrode.
Note: Do not sandblast, wire brush, scrape, or
otherwise service spark plug in poor
condition.
results.
Problem/Condition Means of Identification
Gap-bridged spark Built-up deposits and gap between electrodes
plug closing.
Oil-fouled spark plug Wet, black deposits on the insulator shell, bore,
and electrodes.
Carbon-fouled spark Black, dry, fluffy carbon deposits on insulator
plug tips, exposed shell surfaces and electrodes.
Lead-fouled spark plug Dark gray, black, yellow, or tan deposits; or a
glazed coating on the insulator tip.
Preignition damaged Melted electrodes and possibly blistered
spark plug insulator. Metallic deposits on insulator suggest
internal engine damage.
Overheated spark plug White or light gray insulator with small black or
gray/brown spots with bluish (burned)
appearance on electrodes.
Worn spark plug Severely eroded or worn electrodes.
Figure 3-9 Engine Evaluation Using Spark Plug Condition
TP-6728 10/11
Obtain a new plug for best
6. Check the spark plug gap before installing any
spark plug. See Figure 3-7 and Figure 3-8. Attain
a correct gap when the feeler (or wire) passes
between the spark plug electrode. It should pass
easily but with some resistance or drag; otherwise
adjust as necessary.
Model
15/30 kW
Figure 3-7 Recommended Spark Plug Gap
1. 0.8-0.9 mm (0.031-0.035 in.) gap
2. Spark plug electrodes
Figure 3-8 Spark Plug Gap Inspection
Possible Cause/Solution
Oil or carbon fouling. Clean and regap the spark
plug.
Excessive oil entering combustion chamber
through worn rings and pistons, excessive
clearance between valve guides and stems, or
worn or loose bearings. Replace the spark plug.
Incorrect spark plug, weak ignition, clogged air
intake, overrich fuel mixture, or excessive
no-load operation. Clean and regap the spark
plug.
Caused by highly leaded fuel. Replace the
spark plug.
Wrong type of fuel, incorrect timing or advance,
too hot a plug, burned valves, or engine
overheating. Replace the spark plug.
Engine overheating, wrong type of fuel, loose
spark plugs, too hot a plug, low fuel pressure or
incorrect ignition timing. Replace the spark plug.
Caused by normal wear and failure to replace
spark plug at prescribed interval. Replace the
spark plug.
Section 3 Scheduled Maintenance
Spark plug gap
0.9 mm (0.035 in.)
1
2
1-514
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