If the spark plugs in your car’s engine are not properly maintained you aren’t going to go very far. The spark plugs should be checked every 5 to 6 thousand miles. They should be replaced after 10 to 12 thousand miles. Check your hand-book for the size and grade of your plugs. Always use a spark plug spanner to undo the plugs. A box spanner may damage the fragile ceramic insulator.

Before you can reach the plugs you will first have to remove the HT leads to the distributor. Before you do this label the leads so you know which one fits to which plug. Once you have removed the leads clean off the grit around each plug with an old paint brush. Now take out the plugs with your spark plug spanner. Label the plugs so you know where they go. Take a look at the nodes of the plugs where the electrodes are. A normal plug will have a thin light brown coating over it. Here are some indications that all is not right:

(1) The plug is oiled up. This indicates a worn engine. Try a different grade plug.

(2) The plug is covered with a dry sooty deposit. The fuel / air mix is too high. Check the carburettor setting.

(3) The insulator is spotty. This means that the plug if overheating. Check you have the correct grade.

(4) The threads are damaged. The spark plug has been sitting loosely. Fit a new plug.

If the electrodes have rounded edges then the plug should be replaced. Now you should clean the plugs with a paint brush and white spirit. Dry the plug off and clean the threads and around the outer the outer electrode using a soft wire brush. Use a fine file to clean the working surfaces of the electrodes. Then use a clean cloth to remove any dirt from the outer surface of the insulator.

Check in your handbook for the recommended gap between the spark plug’s electrodes. To set the gap you will need a plug gapping tool. Push the feeler gauge into the gap between the two electrodes. If the gap is correct the feeler will fit quite snugly and you will feel a very slight drag when you pull it out. If the gap is wrong use one of the slots in the gapping tool to bend the side electrode until it is correct.

Reposition the plugs into their holes by hand. Now do them up with the plug spanner, making sure not to cross thread them. Now refit the plug leads, making sure that each one snaps firmly onto the top of it’s spark plug.

Be conscientious with your spark plug maintenance and you will be rewarded with many years of faithful service.