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 installing new wires, replace them one at a time to avoid mix-ups. If it becomes necessary to remove all of the wires from the distributor cap or coil packs at one time, take the time to label the distributor cap/coil pack towers to denote the cylinder number of the wire for that position. When this is done, incorrect positioning of wires can more easily be avoided. Start by replacing the longest one first. Route the wire over the same path as the original and secure in place.
- Disconnect the negative battery cable.
- Note the locations of the spark plug wires, retainers, spark plug and distributor or ignition coil pack.
- If removing all of the spark plug wires, make sure to label the wires and their corresponding positions on the coil or distributor with the proper cylinder number. This will greatly ease installation, preventing much confusion.
- Twist the spark plug boot 1 / 2 turn in each direction before removing, then pull on the boot to remove the wire from the spark plug. Always pull on the boot, never the wire itself.
- Twist the spark plug boot 1 / 2 turn in each direction, then pull the boot to disconnect the spark plug from the distributor or ignition coil, as applicable. Never pull on the spark plug wire, only the plug boot.
- Remove the spark plug wire from any retainers, then remove it from the vehicle.
- Route the wires in the proper location as noted during removal. The wires must be properly routed; you can refer to the accompanying illustrations for spark plug wire routing and retaining clip location.
- Apply a small amount of silicone dielectric compound to the spark plug wire boots and ignition coil or distributor towers.
- Attach the spark plug wire to the to the ignition coil pack or distributor, and spark plug, pushing it on firmly. A click should be felt or heard when the boot is on properly.
- Check that the boot is properly installed by pushing sideways on the installed boots; they should be stiff with only slight looseness. If the boot feels like it-s not on properly, reseat the boot by twisting it 1 / 2 turn, pulling the boot off, then reinstalling the boot.
- Connect the negative battery cable.