Inspection & Gapping
Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%.
Check spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag.
Always check the gap on new plugs as they are not always set correctly at the factory. Do not use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A round-wire type gapping tool is the best way to check the gap. The correct gauge should pass through the electrode gap with a slight drag. If you're in doubt, try one size smaller and one larger. The smaller gauge should go through easily, while the larger one shouldn't go through at all. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely never attempt to bend the center electrode. Also, be careful not to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.
Removal & Installation
When removing spark plugs, remove and install one at a time or label the ignition wires before removal to avoid mixing up the firing order.
If the engine has been run recently allow the engine to cool down before removing spark plugs.
Make sure ignition cables are routed correctly otherwise radio ignition noise, spark plug cross ignition or a short circuit to ground may result.
Always remove the spark plug cable by grasping the top of the spark plug insulator, turning the boot 1 / 2 turn and pulling straight up in a steady motion.
- Disconnect ignition wire from ignition coil.
- Disconnect spark plug cable from spark plug.
- Use compressed air to clear debris from area around spark plug
- Remove the spark plug using a quality socket with a rubber or foam insert.
- Apply thin layer of anti-seize lubricant to spark plug threads.
- To avoid cross threading, start the spark plug into the cylinder head by hand.
Tighten spark plugs to 13 ft. lbs. (17.6 Nm).
CAUTIONThe tapered seat plugs are torque-critical! Do not exceed 13 ft. lbs. (17.6 Nm)!
- Install spark plug insulators over spark plugs. Ensure the top of the spark plug insulator covers the upper end of the spark plug tube.
- Reconnect to coil.