Failure detection

To be located on the engine spark plug, which makes cuts, may be an ordinary pencil. It should sharpen both sides, in the middle to make a cut and remove a piece of slate 3 mm long. One end of the pencil relate to the masses, while others - the electrode spark. If a candle is serviceable, then through an air gap in the lead will slip a spark.

On engines with a classic ignition system sometimes use the following method Validator candles: consistently shoot tips with high-voltage wire from the spark when the engine is running. If a workable off the candle, then the engine speed decreases, if the candle is inoperable, the operation of the engine remains the same.
Attention. You should know that this way of checking is not safe for engines with electronic ignition systems, since it can lead to costly repairs of electronic components.
You can also use another way to verify that the candle. The candle is taken pliers with insulated handles, her body is connected to the negative terminal of the battery, starter motor rotated, sparks in the spark gap is controlled visually.
Applying this method, you should be very careful: from the open spark plug hole knocks fuel mixture. There is one more negative (from my point of view, the most significant): verification is done not with the real pressure and give hundred percent guarantee of performance spark possible.
It happens that the spark plug is working on the form, and even run on a stand shows that everything is in order, however, the problem is in the candle. The fact that even on the stand, where a certain pressure, you can not simulate all operating conditions the spark plug (eg, temperature, vibration, etc.).
Stand for testing spark plugs
In this case, you can check your system with a "test" candles - a known good spark, which is set alternately suspicious instead of spark plugs.