IDLER ASSEM. 1M3935 - Caterpillar

Maintenance of the spark plugs is required to obtain the following benefits:
Normal fuel consumption
Normal levels of emissions
Maximum service life of the spark plugsThe service life of the spark plugs is affected by fouling due to deposits from the oil and by peak voltage. Maintenance of the ignition system is also affected by voltage. Higher voltage is required by higher inlet manifold air pressure and a higher compression ratio. Higher voltage reduces the service life of components such as spark plug wires and transformers.
Ignition systems can cause electrical shocks. Avoid contacting ignition system components and wiring.Do not attempt to remove the valve covers when the engine is operating.
Removing the Spark Plug
Illustration 1 g00823378
(1) Harness connector
(2) Bolt
(3) Transformer
(4) O-ring seal
(5) Extension
(6) Spark plug
Ensure that the mode control switch is in the "STOP" or "OFF/RESET" position.
Pulling on the wiring harness may break the wires. Do not pull on the wiring harness.
Remove the lockwire. Disconnect harness connector (1). Use pliers to turn the connector counterclockwise.
Remove bolts (2).
Remove transformer (3). Inspect O-ring seal (4). If the O-ring seal is worn or damaged, discard the O-ring seal and use a new O-ring seal for assembly.
Remove extension (5).
Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes.
Debris may have collected near the spark plug. Thoroughly remove any debris. Use compressed air. The maximum air pressure for cleaning purposes must be below 207 kPa (30 psi). Ensure that the area around the spark plug is clean and free of dirt and debris.
Use a 4C-4601 Spark Plug Socket and an extension to loosen spark plug (6). After the spark plug has been loosened, remove the spark plug by hand to detect problems with the threads. After the spark plug has been removed, discard the used gasket.
The use of a thread tap will remove metal unnecessarily. This will also reduce the heat transfer for the spark plug. This can result in a reduction of the spark plug service life and a reduction of the detonation margin.
If the spark plug resists removal by hand, apply penetrating oil to the threads. Use the wrench and apply steady pressure to the spark plug until the spark plug is loose.If the spark plug cannot be removed by hand, clean the threads with 9U-7511 Spark Plug Seat Cleaner. This tool scrapes debris from the seat and from the threads.Inspecting the Spark Plug
Illustration 2 g00838300
(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, 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 corona that forms at the top of the shell. The corona develops when a high-voltage potential ionizes the air that surrounds a conductor,