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If the engine is running or the key is in the ON position the ARD plug will continue to fire. Turn the key to the OFF position before servicing the ARD plug. |
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| Illustration 1 | g02139990 |
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(1) Wiring harness
(2) Spark plug | |
- Remove wire harness (1) from spark plug (2).
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Personal injury can result from air pressure.
Personal injury can result without following proper procedure. When using pressure air, wear a protective face shield and protective clothing.
The maximum air pressure for cleaning purposes must be reduced to
205 kPa (30 psi) when the air nozzle is deadheaded. - Debris may have collected in the spark plug well. Thoroughly remove any debris. Use compressed air. The maximum air pressure for cleaning purposes must be below
205 kPa (30 psi) . Ensure that the area around the spark plug is clean and free of dirt and debris. - Use a deep well socket and a breaker bar to loosen the spark plug. If necessary, see your Caterpillar dealer for the part number of the socket. After the spark plug has been loosened, use the socket to remove the spark plug by hand in order to detect problems with the threads. After the spark plug has been removed, inspect the used spark plug and the gasket.
- After removing the spark plug, clean the ground probe inside the ARD combustion head by running a 305-2389 Plug Bore Brush through the hole in the ARD combustion head. This tool scrapes debris from the seat and from the threads. Run the brush through the hole several times.
- Carefully clean the spark plug using a nonmetallic cleaning pad. If the probe appears to be bent, replace the spark plug. Otherwise, install the original spark plug. Refer to Specifications manual for the correct torque value.
Note: The spark plug may be damaged if the spark plug is dropped. Do not install a spark plug that has been dropped.
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Do not use a thread tap. A thread tap will remove metal unnecessarily. The threads could be stripped and the combustion group could be damaged. |
- Ensure that the spark plug is clean and free of dirt and oil.
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NOTICE Do not overtighten the spark plug. The shell can be cracked and the gasket can be deformed. The metal can deform and the gasket can be damaged. The shell can be stretched. This will loosen the seal that is between the shell and the insulator, allowing combustion pressure to blow past the seal. Serious damage to the engine can occur.
Use the proper torque.
- Install the spark plug by hand until the spark plug contacts the ARD. Torque the spark plug to the proper specification. Refer to Specifications, "Spark Plug" for the proper torque specification.
- Connect the wiring harness.
Note: Do not use anti-seize compound on the spark plug. Most of the heat is transferred through the threads and the seat area of the spark plug. Contact of the metal surfaces must be maintained in order to provide the heat transfer that is required.