 |
|
Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring. Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers. |
Maintenance of the spark plugs is required in order to achieve the following benefits:
- Normal fuel consumption
- Normal level of emissions
- Maximum service life of the spark plugs
The 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 plugs, wires, and transformers.
- Remove the three bolts (1) that hold transformer (2) to the valve cover. Leave the wiring attached. Place the transformer out of the way. Do not pull on the wires as damage to the wiring harness could result.
- Remove the spring loaded spark plug extension (3) from the spark plug well.
- Use a
22.23 mm (0.875 inch) , 4C-4601 Spark Plug Socket and an extension to loosen spark plug (4). After the spark plug has been loosened, remove the spark plug by hand in order to detect problems with the threads. After the spark plug has been removed, discard the used spark plug gasket.
| |
| Illustration 1 | g01081802 |
| NOTICE |
|---|
|
Do not use a thread tap. A thread tap will remove metal unnecessarily. The threads could be stripped and the cylinder head could be damaged. |
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 can not 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 in the cylinder head. Be sure to clean any debris from the cylinder.
| |
| Illustration 2 | g00787368 |
|
(1) Terminal post
(2) Insulator (3) Shell (4) Gasket (5) Electrode | |
Inspect 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 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.
| |
| Illustration 3 | g00787372 |
| (6) Precious metal tips on the electrode and the ground strap | |
Caterpillar spark plugs have precious metal tips (6) on 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 around the electrode 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 system
A 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.
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.
- Before installing the spark plug, set the electrode gap. The electrode gap depends on the engine's ignition system.
- For engines with an Altronic ignition system, set the electrode gap to
0.4 mm (0.014 inch) . - For other ignition systems, set the electrode gap to
0.28 mm (0.011 inch) .Adjust the electrode gap, if necessary. Bend the ground strap 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.
Note: Do not use anti-seize compound on spark plugs. Most of the heat is transferred through the threads and the seat area of the spark plug. The surfaces must be in contact in order to provide the heat transfer that is required.
- For engines with an Altronic ignition system, set the electrode gap to
- Ensure that the spark plug is clean and free of dirt and oil.
- Always use a new gasket when a spark plug is installed. If a used spark plug is installed, place a new 9Y-6792 Spark Plug Gasket on the spark plug. Orient the tabs of the gasket toward the electrode. Otherwise, the gasket may not seat properly. If a gasket for a spark plug is installed incorrectly, do not increase the torque on the spark plug in order to improve the seal. Do not reuse the gasket. Install a new gasket.
Show/hide table
NOTICE Do not overtighten the spark plugs. The shell can be cracked and the gasket can be deformed. 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 bottoms out. Tighten the spark plug to
48 ± 4 N·m (35 ± 3 lb ft) . - Install the spark plug extension on the spark plug.
- Center the spark plug extension in the transformer and install the transformer.
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.