Bob. . .
Back in the 60's I worked for an imported car dealer in Glassboro, NJ.
(Among other franchises, we also sold Morgans). Our shop was equipped with a
Champion spark plug cleaner/tester which was bench mounted and connected to
110 v. AC as well as to the shop's compressed air system. To use it, a spark
plug was inserted into the rubber adapter on top and held firmly with one
hand while the other hand activated the jet of air and sand which cleaned
the plug by sand blasting it. After it was cleaned (and then re-gapped), it
was inserted into the electrical test adapter (also part of the machine) and
the high voltage wire connected to the top of the plug. While one hand
pushed a button to fire the plug, the other hand turned an air control valve
to pressurize the chamber around the electrode of the plug. The actual spark
pattern could be viewed "in action" by looking in the mirror. The air
pressure simulated the compression in the cylinder of the engine. If I
recall correctly, we had a booklet of specifications for all plugs which
gave us an idea of how much pressure to apply for each heat range and style
of plug. Naturally, if the plug ceases to fire while under pressure, it will
probably misfire in the engine.
In those days, a prudent shopper could buy spark plugs for less than a
dollar each so, you're right, the labor for cleaning and testing wasn't
worth it. We stopped using the machine for routine services and tune-ups to
avoid comebacks. I hope this was of some help.
Fred Schuchard
63 Plus 4 DHC #5202
fschuch@jaguarsystems.com
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