Spark Plug: Description and Operation

SPARK PLUG
This engine uses resistor spark plugs. For spark plug identification and specifications, refer to Specifications.

Remove the spark plugs and examine them for burned electrodes and fouled, cracked or broken porcelain insulators. Keep plugs arranged in the order in which they were removed from the engine. An isolated plug displaying an abnormal condition indicates that a problem exists in the corresponding cylinder.

Fig.12 Checking Spark Plug Electrode Gap:

Spark plugs that have low mileage may be cleaned and reused if not otherwise defective. Refer to the Spark Plug Condition. After cleaning, file the center electrode flat with a small point file or jewelers file. Adjust the gap between the electrodes to the dimensions specified in the chart by bending the ground electrode just above the attachment weld) with the appropriate tool.

Never apply any force between the electrode or damage to the center electrode assembly will result.

Always tighten spark plugs to the specified torque. Over tightening can cause distortion and damage. Tighten spark plugs to 28 Nm (20 ft. lbs.) torque.

SPARK PLUG CABLE
Spark plug cables are sometimes referred to as secondary ignition wires. The wires transfer electrical current from the coil pack to individual spark plugs at each cylinder. The resistor type, nonmetallic spark plug cables provide suppression of radio frequency emissions from the ignition system.

Check the spark plug cable connections for good contact at the coil and spark plugs. Terminals should be fully seated. The nipples and spark plug covers should be in good condition. Nipples should fit tightly on the coil. Spark plug boot should completely cover the spark plug hole in the cylinder head cover. Install the boot until the terminal snaps over the spark plug. A snap must be felt to ensure the spark plug cable terminal engaged the spark plug.

Loose cable connections will corrode, increase resistance and permit water to enter the coil towers. These conditions can cause ignition malfunction. Plastic clips in various locations protect the cables from damage. When the cables are replaced the clips must be used to prevent damage to the cables, and should be rotated about 300 below the horizontal.