Subsection 03 (IGNITION SYSTEM)
SPARK PLUG
For spark plug replacement procedure, refer to
PERIODIC MAINTENANCE PROCEDURES
sub-
section.
Troubleshooting Fouled Spark Plug
Fouling of the spark plug is indicated by irregular
running of the engine, decreased engine speed
due to misfiring, reduced performance, and in-
creased fuel consumption. This is due to a loss
of compression. Other possible causes are: pro-
longed idling or low-speed riding, a clogged air
filter, incorrect fuel, defective ignition system,
incorrect spark plug gap, lubricating oil entering
the combustion chamber, or too cold spark plug.
The plug face of a fouled spark plug has either a
wet black deposit or a black carbon fouling. Such
coatings form a conductive connection between
the center electrode and ground.
Spark Plug Analysis
A00E0AA
1
2
3
TYPICAL
1. Overheated (light grey, white)
2. Normal (light brown, brown)
3. Fouled (black, wet or dry, dark deposits, grey, melted coating)
The plug face reveals the condition of the engine,
operating condition, method of driving and fuel
mixture. For this reason it is advisable to inspect
the spark plug at regular intervals, examining the
plug face (i.e. the part of the plug projecting into
the combustion chamber).
vmr2016-134
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