LINK 1V7943 - Caterpillar

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.
Illustration 1 g03486537
Location of the ARD spark plug
Prepare the machine for maintenance. Refer to Operation and Maintenance Manual, "Prepare the Machine for maintenance".
Stop the engine.
Allow the exhaust system to cool before performing this procedure.
Raise the hood. Refer to Operation and Maintenance Manual, "Hood Control".
Remove any dirt or debris from the area around ARD spark plug.
Remove spark plug wire from the ARD spark plug.
Use a deep well socket and a breaker bar to loosen the ARD spark plug. If necessary, see your Cat 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 removing spark plug, clean the ground probe inside the ARD combustion head by running a plug bore brush through the hole in the ARD combustion head. 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.Note: The spark plug may be damaged if the spark plug is dropped. Do not install a spark plug that has been dropped.
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. Tighten the spark plug to 43.4 N m (32 lb ft) to 51.5 N m (38 lb ft).
Connect the spark plug wire.
Lower the hood.