Spark Plug: Service and Repair
REMOVALCAUTION: Mark spark plug locations and return to original location.
1. Remove the ignition coil.
2. Remove the spark plug.
3. Inspect the spark plugs for bridged gap.
^ Check for deposit build up closing the gap between the electrodes.
^ Caused by oil or carbon fouling.
^ Clean the spark plug.
4. Inspect for oil fouling.
^ Check for wet black deposits on the insulation shell bore electrodes.
^ Caused by excessive oil entering the combustion chamber through worn rings and pistons, excessive valve stem-to-guide clearance, or worn or loose bearings.
^ Correct oil leakage concern.
^ Replace the spark plug.
5. Inspect for carbon fouling.
^ Identified by black, dry fluffy carbon deposits on insulator tips, exposed shell surfaces and electrodes.
^ Caused by a plug with incorrect heat range, dirty Air Cleaner, too rich a fuel mixture, or excessive idling.
^ Clean spark plug.
6. Inspect for normal burning.
^ Check for light tan or gray deposits on the firing tip.
7. Inspect for pre-ignition.
^ Identified by melted electrodes and possibly blistered insulator.
^ Metallic deposits on the insulator indicate engine damage.
^ May be caused by incorrect ignition timing, wrong type of fuel, or the installation of a heli-coil in place of spark plug threads.
^ Replace the spark plug.
8. Inspect for overheating.
^ Identified by a white or light gray insulator with small black or gray brown spots and with bluish-burnt appearance of electrodes.
^ Caused by engine overheating, wrong type of fuel, loose spark plugs, plug with incorrect heat range, low fuel pump pressure, or incorrect timing.
^ Replace the spark plug.
9. Inspect for fused spot deposits.
^ Identified by melted or spotty deposits resembling bubbles or blisters.
^ Caused by sudden acceleration.
^ Clean spark plug.
10. Adjust the spark plug gap as required.
INSTALLATION
1. Follow the removal procedure in reverse order.
NOTE: Remove any foreign debris from spark plug wells with compressed air.