878382 Mercury CAM

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 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 plugs, wires, and transformers.Remove the Spark Plug
Pulling on the wiring harness may break the wires. Do not pull on the wiring harness.
Standard Ignition System
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Standard ignition system
(1) Cover
(2) Spark plug
Remove cover (1). Ignition Systems With Integral Transformers
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Ignition system with integral transformers
(1) Connector
(2) Clamp
(3) Boot
(4) Transformer
(5) Gasket
Loosen connector (1).
Loosen clamp (2).
Remove boot (3).
Unscrew transformer (4).
Remove gasket (5). Discard the gasket. Removing the Spark Plug
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 in the spark plug well. 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.
To loosen the spark plug, use a 2P-5481 Deep Well Socket. 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.
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 a 154-9521 Spark Plug Seat Cleaner. This tool scrapes debris from the seat and from the threads in the cylinder head.Inspecting the Spark Plug
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(1) Terminal post
(2) Insulator
(3) Shell
(4) Gasket
(5) Electrode and ground straps 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, 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 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.Inspect the electrode and ground straps (5) for excessive wear. Flat surfaces with sharp edges provide the best conditions for creating a spark. An electrode will become worn from use. The surfaces erode. A higher voltage is required in order to produce a spark.Cat spark plugs have precious metal tips on the electrode and the ground straps. This material will gradually erode. Use extreme care for setting the electrode gap. Maintain even spacing between the two ground straps and the electrode.Replace the spark plug if the precious metal is worn off.Normal operation will produce a light brown deposit around the electrode.White deposits or gray deposits 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 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.Cleaning the Spark Plug
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.Installing the Spark Plug
Note: Do not use a flat feeler gauge for measuring the electrode gap of used spark plugs. A feeler gauge will falsely measure the actual electrode gap. This is due to the curvature of the used precious metal surfaces.
Before installing the spark plug, set the electrode gap to 0.635 0.025 mm (.0250 .0010 inch). Use the 9U-7516 Spark Plug Gauge. Adjust the electrode gap in order to achieve proper alignment and even spacing between the 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.
Ensure that the spark plug is clean and free of dirt and oil.
Always use a new gasket when a s