Cleaning spark plugs

by Had Robinson

Why not get a wire brush and go after the deposits on the spark plug so it will work like new?

Trouble is – that is not what happens.  The only way to clean a spark plug is with a special sand blaster and most home shops do not have one.  When the plug is cleaned with a wire brush (of any metal type) a microscopic layer of metal is deposited all over the plug, including the white insulator near the tip.

The accumulation of anything conductive in that area shorts the plug out.  A sure sign of a fouled/ruined spark plug is to remove the plug, reattach the secondary wire, and spin the engine.  If it is dark enough it is easy to see the spark scatter across the surface of the insulator instead of going to grounded electrode.

I occasionally see plugs that have been wire-brushed and the pilot wonders why the engine does not run?  The plug below looks perfect but it is fouled from cleaning and is shorted out and useless.

fouled spark plug

Solution is always buy a new plug unless you have the special sand blaster.  The only exception would be if you have an ultrasonic cleaner (UC) and you live in a country where sparkplugs are expensive or hard to obtain.  The UC will remove plug fouling effectively and then you may use a thin file (NOT SANDPAPER) to dress the electrodes.  Sharp edges are more effective in igniting the air-fuel mixture.  This all takes some time, however.  In the U.S. and some countries, it is not worth the time or effort to clean and adjust spark plugs.