7.1.6. Engine diagnostics on a condition of spark plugs

The condition of the engine can be estimated by the form deposits on an insulator of the central electrode.

Fig. 7.6. Defect of an insulator

Connect a candle wire of a high voltage to the spark plug which has been turned out from a head of cylinders. Connect an external electrode (case) of a candle to "weight" (with an arm on the engine), scroll a cranked shaft of the engine a starter. If the candle is serviceable, between electrodes of a spark plug the spark (quite weak as the category passes in the atmosphere at a small gap) will slip. If the spark plug is faulty, the spark will not appear because of leakage of a charge on a candle insulator (fig. 7.6).

Check a cap and wire isolation on lack of cracks.

Fig. 7.7. Scheme of measurement of resistance of a candle wire

Measure resistance of a wire (fig. 7.7).

NOTE Resistance of a candle wire of a high voltage should not be higher than 10 kiloohms (BOUGI) or 22 kiloohms (R16AIPS) on meter of length of a wire. If resistance of a wire is higher than the specified size, replace a wire.