Spark Plug: Service and Repair

REMOVAL
1. Grasp the spark plug boot firmly and use a twisting, pulling motion to disconnect the spark plug wires from the spark plugs.

CAUTION: Spark plug wires must be connected to the correct ignition coil terminal and spark plug. Mark the spark plug wire locations.







2. Remove the spark plugs.

NOTE: Remove any foreign materials from the spark plug wells with compressed air before removing the spark plugs.







3. Inspect the spark plugs for a bridged gap.
^ Check for deposit build-up closing the gap between the electrodes. Deposits are caused by oil or carbon fouling.
^ Clean the spark plug.







4. Check for oil fouling.
^ Check for wet, black deposits on the insulator shell bore electrodes, caused by excessive oil entering the combustion chamber through worn rings and pistons, excessive valve-to-guide clearance or worn or loose bearings.
^ Correct the oil leak concern.
^ Install a new spark plug.







5. Inspect for carbon fouling
^ Look for black, dry, fluffy carbon deposits on insulator tips, exposed shell surfaces and electrodes, caused by a spark plug with a incorrect heat range, dirty air cleaner, too rich fuel mixture or excessive idling.
^ Clean the 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 a possibly damaged insulator. Metallic deposits on the insulator indicate engine damage. This may be caused by incorrect ignition timing, wrong type of fuel or the installation of a heli-coil insert in place of the spark plug threads.
^ Install a new spark plug.







8. Inspect for overheating identified by a white or light gray-brown spots and white bluish-burnt appearance of electrodes. This is caused by engine overheating, wrong type of fuel, loose spark plugs, spark plugs with a incorrect heat range, low fuel pump pressure or incorrect ignition timing.
^ Install a new spark plug.







9. Inspect for fused deposits, identified by melted or spotty deposits resembling bubbles or blisters. These are caused by sudden acceleration.
^ Clean the spark plug.







10. Adjust the spark plug gap as required.

INSTALLATION







1. To install, reverse the removal procedure.

NOTE: Apply Silicone Brake Caliper Grease and Dielectric Compound D7AZ-19A331-A or equivalent meeting Ford specification ESE-M1C171-A to the inside of the spark plug wire boots.