SHIM 3088777 - Caterpillar

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Typical spark plug with a single ground strap (1) Terminal post (2) Insulator (3) Shell (4) Gasket (5) Electrode
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Section view and bottom view of a spark plug with two ground strapsInspect the spark plug closely for damage. The condition of the spark plug can indicate the operating condition of the engine.Inspect insulator (2) for cracks. If a crack is found, discard the spark plug.Faint marks may extend from shell (3) onto the insulator. The marks may be a result of a corona that forms at the top of the shell. The conductor will develop a corona when a very high voltage potential ionizes the air. This is a normal condition. This is not an indication of leakage between the shell and the insulator.Inspect shell (3) for damage. Cracks can be caused by overtightening the spark plug. Overtightening can also loosen the shell. Discard any spark plug that has a shell that is cracked or loose.Caterpillar spark plugs have precious metal tips on the ends of the electrodes. This material will gradually erode. Use extreme care when you set the electrode gap. Maintain even spacing and proper alignment between the precious metal surfaces.Replace the spark plug if the precious metal is worn off.A light brown deposit or a beige deposit is produced by normal operation.Deposits that are gray or black may be caused by the following substances:
Excessive oil
Use of the wrong oil
A substance that is introduced through the fuel system or the air systemA spark plug can operate despite a buildup of ash. However, a buildup of ash can cover the electrode gap. This will cause misfire. Large deposits may retain heat which can cause premature fuel ignition. This can lead to uncontrollable detonation.Cleaning the Spark Plug
Thoroughly clean the spark plug. Do not use a wire brush. Glass beads are the preferred method for cleaning.Follow these guidelines for using glass beads:
Always use clean glass beads.
Use care in order to clean only the electrode and the insulator near the electrode.
Do not use glass beads on the outside of the shell or on the upper part of the insulator.Checking the Spark Plug
After the spark plug is clean, measure the spark plug's electrode gap.Note: Use the 9U-7516 Spark Plug Gauge to measure the electrode gap. Do not use a flat feeler gauge for measuring the electrode gap of used spark plugs. A feeler gauge will incorrectly measure the actual electrode gap because the used precious metal tips are curved.Adjust the electrode gap by bending the ground electrode at the existing bend. Then bend the strap near the weld in order to achieve proper alignment and even spacing between the two precious metal surfaces. Measure the electrode gap after the alignment. Correct the electrode gap, if necessary.For low emission engines, adjust the electrode gap to 0.28 mm (0.011 inch).For stoichiometric engines, adjust the spark plug gap to 0.38 mm (0.015 inch).Installing the Spark Plug
Note: Do not use anti-seize compound on spark plugs. Most of the heat is transferred through the threads