CYLINDER GP-BULLDOZER LIFT 4176242 - Caterpillar

Removing the Spark Plug
Before removing a spark plug, ensure that the area around the spark plug is clean and free of dirt and debris.
Always use a spark plug socket to remove spark plugs. Use a 9S-5031 Spark Plug Socket for 14 mm spark plugs. Use a 4C-4601 Spark Plug Socket for 18 mm spark plugs. After the spark plug has been loosened, try to remove the spark plug by hand in order to detect problems with the threads.
If it is difficult to remove the spark plug by hand, use the appropriate tool to clean the threads in the cylinder head that are for the spark plug. Use the 9U-7511 Spark Plug Seat Cleaner for spark plugs with 18 mm thread. Use the 154-9521 Spark Plug Seat Cleaner for spark plugs with 14 mm thread. Be sure to clean any debris from the cylinder.Note: Do not use a thread tap to clean the threads in the cylinder head that are for the spark plug. A thread tap will remove metal unnecessarily. This practice will eventually result in the failure of the threads in the cylinder head that are for the spark plug.Inspecting the Spark Plug
Illustration 1 g00778942
(1) Terminal post (2) Insulator (3) Shell (4) Gasket (5) ElectrodeInspect the spark plug closely for damage. The condition of the spark plug can indicate the operating condition of the engine.Terminal post (1) must not move. If the terminal post can be moved by hand, carefully tighten the post into the threads of the insulator. If the post cannot be tightened, discard the spark plug.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. See Engine News, SEBD9262, July 1998, "Effects Of Corona On Spark Plugs" for additional information.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.
Illustration 2 g00778946
(6) Precious metal tips on the electrode and the ground strapCaterpillar spark plugs have precious metal tips (6) on the ends of the electrode and the ground strap. This material will gradually erode. Use extreme care when you set the electrode gap. Maintain even spacing and proper alignment between the two 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