You will need: a special wrench for removing spark plugs, a set of round probes.
1. Remove tips from candles. Clean the spark plug and the area around it of dirt so that when the spark plug is turned out, dirt does not get into the cylinder.
2. Loosen the spark plugs and remove the spark plugs from the cylinder head.
3. Inspect the candles. If there are cracks on the insulators, threads or electrodes are damaged, the candles must be replaced.
Light brown soot, evenly covering the lower part of the candle with a thin layer, does not affect the operation of the ignition system, it can not be cleaned off.
The absence of carbon deposits on the candle indicates either the operation of the engine on a lean mixture, or an incorrectly set ignition timing, or a discrepancy between the brand of the candle and the type of engine.
Shiny black soot is a sign of oil getting into the engine cylinder. Such a candle must be cleaned.
4. Check the gap between the spark plug electrodes (only round probe). For carburetor engines, it should be 0.7-0.85 mm, for engines with an injection system - 1.00-1.13 mm.
5. If the gap differs from the specified, adjust it by bending the side electrode.
6. When installing candles, first wrap them by hand, and then tighten them with a wrench. Do not exceed torque.
Helpful Hints: Gone are the days when the question «What candles to buy?» was irrelevant and it was possible to purchase only domestic and only the same model as on the car. Now on the shelves there is a huge selection of candles from almost all foreign manufacturers. And naturally «self-punchers» immediately began to fake them.
In order not to buy such candles, first of all, pay attention to the packaging - the quality of printing from real manufacturers is impeccable, while for fake ones, the contours of the drawings often do not match. If there is no packaging at all, further inspection of the candles does not make sense - there are no branded candles without it.
Then inspect the candles. The central electrode must have a clear cylindrical shape, and its surface must be absolutely smooth. If there are defects on the electrode, and even more so if it is crooked, then you have a fake.
The side electrode of a fake candle is often also welded crookedly, and its edges are oblique. For branded candles, the thread is knurled, so it is absolutely smooth. For fake ones, it is cut and has small chips.
The sealing ring of a real spark plug cannot be removed. In a fake one, it is either screwed along the thread, or easily removed.
The insulator of a real candle is absolutely smooth and shiny. A fake often shows longitudinal seams from an inaccurately docked mold.
Finally, the inscription on the insulator must be clear, even and neat.
And lastly, real branded candles cannot be cheap. Too low a price should alert you.
Sometimes during intensive acceleration with «promotion» engine, almost to maximum speed, sharp jerks appear, perceived as blows. Spark plugs are to blame, although checking with a piezo tester («pistol») talks about their goodness. The reason is that spark plugs lose their tightness over time and a spark plug that works normally at low and medium loads at high pressure in the combustion chambers misfires. Therefore, it is not recommended to operate candles without replacement for more than 15 thousand km.