Spark plug maintenance - how to check, clean, or replace

Jan 6, 2021 3 min read
Spark plug maintenance - how to check, clean, or replace

Spark plug helps the car engine to start and keep running with maximum efficiency. Flawed spark plug can cause starting problems and decreased fuel efficiency.

Spark plug is used to deliver electric current from an ignition system to the combustion chamber of an ignition engine to excite the compressed fuel mixture by an electric spark. It has a metal threaded shell which is electrically isolated by a ceramic insulator from a central electrode. This central electrode may restrain a resistor which is linked by a heavily insulated wire to output terminal of an ignition coil. The metal is screwed into the cylinder heads of the engine and hence electrically grounded. Resulting in forming one or more spark gaps between the inner ends of central electrode, the central electrode expands through the porcelain insulator into the combustion chamber. Generally one or more structures are attached to the inner end of the metal shell and assigned as the side, earth or ground electrode(s).

Checking spark plugs of a car

The dirty spark plugs take more voltage. The electrodes of spark plug should be clean to produce the powerful spark required for ignition. Tugging repeatedly and continuously on the rewind to start the engine, or a damaged spark plug may cause excessive fuel consumption, deposits on the cylinder head and oil dilution.

How to check for damaged spark plug?

• Disconnect the spark plug and clean the area around the plug to avoid getting slag in the combustion chamber when the plug is removed

• With the help of spark plug socket, remove the spark plug

• Clean the deposits from the plug with wire brush and spray-on plug cleaner

• Check the spark plug for mulish deposits, or for cracked porcelain or burned electrodes. If one of these conditions continues to prevail, then replace the spark plugs.

• Check the spark plug gap  and adjust them

• If it is not working, replace the spark plug (don’t over tighten) and reattach the spark plug lead. Then start the engine.

How to clean the spark plug?

Over the course of daily explosions, there is a normal build-up of grit which gets accumulated on the spark plugs. Spark plugs can be cleaned by many ways such as:-

With sand paper

• Fold the sandpaper into half and glide it between the electrode and arm, if the gap on the plug is larger.  Gently remove the deposit present there.

• Do not force if the gap isn't that big to slide a folded sandpaper then use it as it is but clean both arm and electrode.

• Clean the area between the electrode and the insulator to clean the debris from the groove. We should use something like pin to reach into the groove.

• Flip the spark plug to dust of the sand from the electrode and arm.

With grit blasting

• Many auto shops and garages keep grit blasting equipment and clean spark plugs. There is a rubber seal which holds the plug and even the dirtiest plug is cleaned within minutes.

With a quick drying liquid

• Remove the visible dirt from the spark plug using a clean rag

• To remove remaining deposits use a wire brush

• We can use mineral spirit, 90% alcohol or carburetor/injector to clean the firing end of the spark plug. When applying cleaner on the spark plug, wear gloves and eye protection and dry it well.

Restore the gap

After removing the debris from the plug with the help of sandpaper, grit blasting and/or quick drying liquid and we should fix the gap.

• Check the manual for the gap measurement recommended for the particular vehicle.

• Pass a gapper through the space between the electrode and the arm to set the gap.

• The gapper should not stick or click instead it should touch both sides when it slides through.

• Adjust the height of the arm, if it sticks or clicks.

• Close the gap slightly if it doesn't touch both electrode and arm.

• Resume the work when the gap is settled.

How to replace spark plug of a car

Firstly, check that the threads of the spark plug are clean before placing them back into the holes. Tightening these spark plugs is very important. We should make it tight but not over-tight that the washer becomes flattened and ineffective. Replace the spark plug ignition coil and wiring connector. The rubber boot may need a coat of dielectric grease on the inside for easy removal next time. Repeat these steps of removal and installation process for each spark plug.

Hope, above procedures will help you keep the spark plugs of your car in good shape.

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