Spark plug performance can be greatly impacted by the installation process. By closely paying attention during the removal and installation procedure many field issues from short life to product failure can be avoided. Spark plug removal and installation should always be done by hand. This will enable the technician to determine if any loose or binding conditions exist. If the spark plug seems to be overly tight either on removal or during installation engine deposits built up over time are the most common reason. Mechanics should take the following steps to ensure proper fit if tightness is observed.
Use the appropriate thread chasing tool to clean out threads. Heavy grease should be applied to the flutes to catch any debris.
Gasket seating area should be wiped clean to ensure proper seating area.
Install plugs by hand all the way to the gasket. If resistance is found, remove the plug and follow steps 4-6 for using bottom hole taps.
Determine the appropriate thread size for the application. Failure to use the correct tap will result in damage to the spark plug port.
Apply heavy grease to the flutes of the tap to catch any debris that will be removed from the thread area and run the tap completely through the threads.
Reinstall plug by hand and then torque to the appropriate specifications.
In some applications, it may be very difficult to use bottom hole taps in the field. Several tool manufacturers offer specialized wire clean out tools that may allow debris to be cleaned without the threat of damaging the spark plug port. In applications where this is the only alternative, if the cleanout cannot be accomplished, cylinder heads will need to be removed to bring the ports back to SAE specifications. If looseness is detected upon installation, necessary steps must be taken to correct the problem. Failure to address this condition can result in torching or failure due to lost heat transfer. GPG recommends that spark plug ports be checked every 6 months or every spark plug change if the PM interval is 6 months or longer.
