Dodge dakota 2002 Service Manual page 486

DR
SPARK PLUG (Continued)
mal in condition and can be cleaned using standard
procedures.
Fig. 45 SCAVENGER DEPOSITS
1 - GROUND ELECTRODE COVERED WITH WHITE OR YELLOW
DEPOSITS
2 - CENTER ELECTRODE
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator
from the center electrode (Fig. 46). Spark plugs with
this condition must be replaced.
Fig. 46 CHIPPED ELECTRODE INSULATOR
1 - GROUND ELECTRODE
2 - CENTER ELECTRODE
3 - CHIPPED INSULATOR
PREIGNITION DAMAGE
Preignition damage is usually caused by excessive
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis-
solves somewhat latter (Fig. 47). Insulators appear
relatively deposit free. Determine if the spark plug
has the correct heat range rating for the engine.
IGNITION CONTROL
Determine if ignition timing is over advanced or if
other operating conditions are causing engine over-
heating. (The heat range rating refers to the operat-
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specific
temperature ranges. This depends upon the thick-
ness and length of the center electrodes porcelain
insulator.)
Fig. 47 PREIGNITION DAMAGE
1 - GROUND ELECTRODE STARTING TO DISSOLVE
2 - CENTER ELECTRODE DISSOLVED
SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
48). The increase in electrode gap will be consider-
ably in excess of 0.001 inch per 2000 miles of opera-
tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
timing, detonation and cooling system malfunctions
can also cause spark plug overheating.
Fig. 48 SPARK PLUG OVERHEATING
1 - BLISTERED WHITE OR GRAY COLORED INSULATOR
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