Spark Plug Inspection
Spark Plug Usage
1. |
Ensure that the correct spark
plug is installed. An incorrect spark plug causes driveability
conditions. Refer to the electronic parts catalog for the correct
spark plug. |
2. |
Ensure that the spark plug has
the correct heat range. An incorrect heat range causes the
following conditions: |
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• |
Spark plug fouling-Colder
plug |
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Pre-ignition causing spark
plug and/or engine damage-Hotter plug |
Spark Plug Inspection
1. |
Inspect the terminal post (1)
for damage. |
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• |
Inspect for a bent or broken
terminal post (1). |
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Test for a loose terminal post
(1) by twisting and pulling the post. The terminal post (1) should
NOT move. |
2. |
Inspect the insulator (2) for
flashover or carbon tracking, soot. This is caused by the
electrical charge traveling across the insulator (2) between the
terminal post (1) and ground. Inspect for the following
conditions: |
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• |
Inspect the spark plug boot
for damage. |
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• |
Inspect the spark plug recess
area of the cylinder head for moisture, such as oil, coolant, or
water. A spark plug boot that is saturated causes arcing to
ground. |
3. |
Inspect the insulator (2) for
cracks. All or part of the electrical charge may arc through the
crack instead of the electrodes (3, 4). |
4. |
Inspect for evidence of
improper arcing. |
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• |
Measure the gap between the
center electrode (4) and the side electrode (3) terminals. Refer to
Ignition System Specifications . An excessively wide electrode
gap can prevent correct spark plug operation. |
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• |
Inspect for the correct spark
plug torque. Refer to
Ignition System Specifications . Insufficient torque can
prevent correct spark plug operation. An over torqued spark plug,
causes the insulator (2) to crack. |
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• |
Inspect for signs of tracking
that occurred near the insulator tip instead of the center
electrode (4). |
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• |
Inspect for a broken or worn
side electrode (3). |
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• |
Inspect for a broken, worn, or
loose center electrode (4) by shaking the spark plug. |
5. |
A rattling sound indicates
internal damage. |
6. |
A loose center electrode (4)
reduces the spark intensity. |
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• |
Inspect for bridged electrodes
(3, 4). Deposits on the electrodes (3, 4) reduce or eliminates the
gap. |
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Inspect for worn or missing
platinum pads on the electrodes (3, 4) If equipped. |
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Inspect for excessive
fouling. |
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• |
Inspect the spark plug recess
area of the cylinder head for debris. Dirty or damaged threads can
cause the spark plug not to seat correctly during
installation. |
Spark Plug Visual Inspection
1. |
Normal operation-Brown to
grayish-tan with small amounts of white powdery deposits are normal
combustion by-products from fuels with additives. |
2. |
Carbon Fouled-Dry, fluffy
black carbon, or soot caused by the following conditions:
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• |
Excessive fuel pressure
|
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Restricted air filter
element |
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Reduced ignition system
voltage output |
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Incorrect spark plug
gap |
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Excessive idling or slow
speeds under light loads can keep spark plug temperatures so low
that normal combustion deposits may not burn off. |
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Deposit Fouling-Oil, coolant,
or additives that include substances such as silicone, very white
coating, reduces the spark intensity. Most powdery deposits will
not effect spark intensity unless they form into a glazing over the
electrode. |
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