Isuzu I-280, I-350 2005-06

Spark Plugs

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Inspection



  1. Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions.
  2.  
  3. Ensure that the spark plug has the correct heat range. An incorrect heat range causes the following conditions:

    Spark plug fouling-Colder plug
     
    Pre-ignition causing spark plug and/or engine damage-Hotter plug
     

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  1. Inspect the terminal post (1) for damage.

    Inspect for a bent or broken terminal post (1).
     
    Test for a loose terminal post (1) by twisting and pulling the post. The terminal post (1) should NOT move.

    Click image to see an enlarged view

    Fig. Inspecting spark plug

     

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  3. 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:

    Inspect the spark plug boot for damage.
     
    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.
     

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  5. Inspect the insulator (2) for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes (3, 4).
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  7. Inspect for evidence of improper arcing.

    Measuring the gap between the center electrode (4) and the side electrode (3) terminals. An excessively wide electrode gap can prevent correct spark plug operation.
     
    Inspect for the correct spark plug torque. Insufficient torque can prevent correct spark plug operation. An over torqued spark plug, causes the insulator (2) to crack.
     
    Inspect for signs of tracking that occurred near the insulator tip instead of the center electrode (4).
     
    Inspect for a broken or worn side electrode (3).
     
    Inspect for a broken, worn, or loose center electrode (4) by shaking the spark plug. A rattling sound indicates internal damage. A loose center electrode (4) reduces the spark intensity.
     
    Inspect for bridged electrodes (3, 4). Deposits on the electrodes (3, 4) reduce or eliminates the gap.
     
    Inspect for worn or missing platinum pads on the electrodes (3, 4), if equipped.
     
    Inspect for excessive fouling.
     
    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.
     

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  1. Normal operation-Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with additives.
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  3. Carbon fouled-Dry, fluffy black carbon, or soot caused by the following conditions:

    Rich fuel mixtures: Leaking fuel injectors, excessive fuel pressure, restricted air filter element, incorrect combustion.
     
    Reduced ignition system voltage output: Weak coils, worn ignition wires, incorrect spark plug gap
     
    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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  5. Deposit fouling-oil, coolant, or additives that include substances such as silicone, very white coating reduces the spark intensity. Most powdery deposits will not affect spark intensity unless they form into a glazing over the electrode.
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Inspection & Gapping



The ignition timing is preset and cannot be adjusted.

Removal & Installation



  1. Remove the ignition coils.
    CAUTION
    Wear safety glasses when using compressed air, as flying dirt particles may cause eye injury.


    WARNING
    Clean the spark plug recess area before removing the spark plug. Failure to do so could result in engine damage because of dirt or foreign material entering the cylinder head, or by the contamination of the cylinder head threads. The contaminated threads may prevent the proper seating of the new plug. Use a thread chaser to clean the threads of any contamination.

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  3. Clean the spark plug recesses with low pressure air.
    CAUTION
    Allow the engine to cool before removing the spark plugs. Attempting to remove the spark plugs from a hot engine may cause the plug threads to seize, causing damage to cylinder head threads.

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  5. Remove the spark plugs from the cylinder head.
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  7. Inspect the spark plugs.

    Click image to see an enlarged view

    Fig. Removing and installing spark plugs

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To install:


WARNING
Use only the spark plugs specified for use in the vehicle. Do not install spark plugs that are either hotter or colder than those specified for the vehicle. Installing spark plugs of another type can severely damage the engine.


WARNING
Check the gap of all new and reconditioned spark plugs before installation. The pre-set gaps may have changed during handling. Use a round feeler gage to ensure an accurate check. Installing the spark plugs with the wrong gap can cause poor engine performance and may even damage the engine.

  1. Measure the spark plug gap on the spark plugs to be installed. Compare the measurement to the gap specifications, 0.042 in (1.08 mm).
    WARNING
    Be sure that the spark plug threads smoothly into the cylinder head and the spark plug is fully seated. Use a thread chaser, if necessary, to clean threads in the cylinder head. Cross-threading or failing to fully seat the spark plug can cause overheating of the plug, exhaust blow-by, or thread damage.

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  3. Install the spark plugs to the cylinder head. Tighten the spark plugs to 13ft. lbs. (18 Nm).
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  5. Install the ignition coils.
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