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Window into the ( car's ) soul

Question : MY friends tell me that a spark plug replacement device can be used to tune the air-fuel mixture on my carbureted 1980 Mercedes Benz 190E.

I have never heard of a device and I am unable to find any literature on it.

Does such a device exist and, if so, is it a useful addition to the DIY toolbox?

Answer : SUCH a device certainly does exist and is manufactured by a company named Gunsons in the United Kingdom.

The device is known as Colortune and is a spark plug with a quartz window.

The Colortune device is fitted in place of one of your engine's spark plugs and the colour of the combustion flame is observed through the quartz window.

The mixture is adjusted until the flame turns blue, indicating that the mixture is at an optimum.

A word of warning though -- the degree of accuracy achieved by this method of tuning is unlikely to be highly precise although, in most cases, it should suffice for older vehicles.

It is, however, a useful and relatively inexpensive addition to the home mechanic's toolbox.


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Judging the air-fuel ratio

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Spark plugs poser

Soiled plugs, tired engine

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Not too hot, not too cold

Get the spark right

Glow and new glory

Window into the ( car's ) soul

Clogged plugs

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Up in smoke


Spark plugs
Timing belt


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