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Checking and replacing the spark plugs (petrol engines)
To remove and install the spark plugs use a special candle key. Before removing the spark plugs allow the engine to cool and clean the brush candles in niches around the cylinder head. Replace only with the manufacturer's recommended candles. On gasoline engines mounted candle following brands and their analogues: When you reinstall or install new spark, check the electrode (spark) gap and adjust it (if it is controlled manually). To do this, bend or bend the side electrode. Before removing the high-voltage wires from spark plugs put on them the label marker, then to connect them properly. When removing the wires, pull only the tip. Remove the spark plug check and then, if it is re-established, clear brush and (or) blow compressed air.
| Fig. 2.4. The normal state of the spark plug
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In appearance, the candle can be judged on the conditions of its operation and the condition of the engine. Candle (Fig. 2.4) operating under normal conditions, is brown or grayish-yellow color of the insulator and electrodes.
| Fig. 2.5. Soot deposits on the spark plug
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The deposition of the dry carbon black (soot) (Fig. 2.5) indicates a rich fuel-air mixture or after the ignition. This leads to misfire, difficulty starting and erratic engine. At the same time, check and, if necessary, replace the air filter, check and adjust the level of fuel in the carburetor float chamber (carburettor engines), and installation of the moment of ignition.
| Fig. 2.6. Oil deposits on the spark plug
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Oil deposits (Fig. 2.6) on the electrodes and the insulator caused by the ingress of oil into the combustion chamber through the valve guides or via the piston rings. This is accompanied by hard starting engine, omissions in the cylinder and the twitching of a running engine (its unstable work).
| Fig. 2.7. Erosion of the electrodes of the spark plug
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Glossy white insulator of the central electrode, burned electrodes and the absence of sediment (Fig. 2.7) are symptoms of overheating candles, which shortens its life. The reasons for the discrepancy may be the type of candles, recommended for the engine pre-ignition, lean mixture, air leak in the intake manifold. Engine overheating and thus overheating of candles can be caused by insufficient coolant and radiator plugging.
| Fig. 2.8. Melting electrode spark plugs
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Melted electrodes, white insulator (or dirt gets on his deposits from the combustion chamber at a misfire) (Fig. 2.8) suggest an early ignition. It is necessary to check that the type of the spark plugs, ignition timing setting, the composition of the fuel-air mixture operation of cooling and lubrication.
| Fig. 2.9. Change the color of the insulator
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Yellowish insulator glazed (Fig. 2.9), indicating a significant increase in temperature in the combustion chamber with a sharp acceleration of the vehicle. The deposits on the spark becomes conductive - it causes gaps in sparking at high speeds. You must install new spark plugs.
| Fig. 2.10. Electrode bridge
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Deposits scored spark gap and formed a bridge between the electrodes (Fig. 2.10). In this case, a candle and the cylinder ceases to operate off of work. It is necessary to remove deposits between the electrodes or replace the spark plug.
| Fig. 2.11. Deposition of additives on the electrodes
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A large number of light-brown sediments crusted central and side electrodes (Fig. 2.11) lead to the isolation of the electrodes, causing gaps in sparking and faults in the engine during acceleration. They can be isolated from additives to the oil or gasoline. If an excessive amount of fat produced in a short time or low mileage, replace the valve seals. Also, a possible reason is the low quality of gasoline, in this case, you must change their place of refueling.
| Fig. 2.12. Wear electrodes
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Candles with rounded electrodes with a small amount of deposits on them and normal color (Fig. 2.12) may lead to difficulty in starting the engine cold or wet weather and to deterioration of fuel efficiency. You should replace the spark for new ones with the same characteristics.
| Fig. 2.13. Cracked or chipped insulator
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Cracked or chipped insulator (Fig. 2.13) indicates the detonation combustion of fuel. Fragments of the insulator can cause damage to the piston. You should replace the spark; verify fuel use with the desired octane; adjust the ignition timing.
| Fig. 2.14. Nagar-on-insulator
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Nagar candle sticks to the insulator (Fig. 2.14), looking up from the bottom of the piston or the wall of the combustion chamber at high engine speeds. It is necessary to clean the candles or to replace them with new ones.
| Fig. 2.15. Mechanical damage to the spark plug
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Mechanical damage candles (fig. 2.15) may be caused by foreign objects trapped in the combustion chamber. This leads to the destruction of the candle, disconnection and damage of the piston cylinder. It is necessary to remove a foreign object from the cylinder, and (or) replace the spark plug. Before reinstalling spark plugs, clean the thread and check the integrity of all the strands of thread. During installation, the absence of skew candles. For ease of installation, insert the candle in the scrap rubber hose and screw it a few turns of the end of the hose. Then tighten the spark plug wrench. The tightening torque of the spark plugs 25 Nm. Description of other work performed in the maintenance of the car, can be found in the relevant sections.
Spark plug
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