To removal and installation of spark plugs apply a special candle key. Before removal of spark plugs let's the engine cool down and clear a niche brush around candles in a head of the block of cylinders. When replacing use only the candles recommended by manufacturer. Install candles of the following brands and their analogs on petrol engines:

At repeated installation or installation of new candles check an interelectrode (spark) gap and adjust it (if it is regulated manually). For this purpose unbend or turn in a side electrode.

Before removal of high-voltage wires from spark plugs make them tags a marker that then it is correct to connect them. At removal of a wire pull only for its tip.

Examine the removed candle, and then if it is repeatedly established, clear a brush and (or) blow compressed air.

Fig. 2.4. Normal state of a spark plug

On appearance of a candle it is possible to judge conditions of its work and a condition of the engine. The candle (fig. 2.4) working in normal conditions has brown or grayish-yellow color of the insulator and electrodes.

Fig. 2.5. Deposits of soot on a spark plug

Adjournment of dry soot (soot) (fig. 2.5) indicates rich fuel-air mix or late ignition. It leads to admissions of ignition, the complicated launch and unstable operation of the engine. At the same time check and if necessary replace the air filter, check and adjust fuel level in the float-operated camera of the carburetor (carburetor engines), and installation of the moment of ignition.

Fig. 2.6. Oil deposits on a spark plug

Oil deposits (fig. 2.6) on electrodes and the insulator are caused by hit of oil in the combustion chamber via the directing plugs of valves or through piston rings. At the same time the complicated launch of the engine, admissions in operation of the cylinder and twitching of the working engine (its unstable work) is observed.

Fig. 2.7. Obgoraniye of spark plug electrodes

The glossy white insulator of the central electrode, the burned electrodes and lack of deposits (fig. 2.7) are candle overheat symptoms which reduces its resource. Discrepancy like candle, early ignition, poor mix, the air suction recommended for this engine in the inlet pipeline can be the reasons. The overheat of the engine and, respectively, an overheat of candles can be caused by the insufficient level of cooling liquid and a contamination of a radiator.

Fig. 2.8. Oplavleniye of spark plug electrodes

The melted-off electrodes, the white isolation center (or the polluted deposits getting on it from the combustion chamber at the admission of ignition) (fig. 2.8) testify to early ignition. At the same time it is necessary to check compliance like spark plugs, installation of the moment of ignition, composition of fuel-air mix, operation of cooling systems and lubricant.

Fig. 2.9. Change of color of the insulator

The yellowish insulator covered with glaze (fig. 2.9) indicates substantial increase of temperature in the combustion chamber at sharp acceleration of the car. Deposits on a candle become conducting — it causes admissions in sparking at high speeds. It is necessary to establish new spark plugs.

Fig. 2.10. Interelectrode bridge

Deposits hammered a spark gap and formed the bridge between electrodes (fig. 2.10) . In this case the candle ceases to work and the cylinder is switched off from work. It is necessary to remove deposits between electrodes or to replace a candle.

Fig. 2.11. Deposits of additives on electrodes

A large number of the light brown deposits covering with a crust the central and side electrodes (fig. 2.11) is led to isolation of electrodes, cause admissions in sparking and interruption in operation of the engine at dispersal. They can be allocated from additives to oil or gasoline. If the excessive number of deposits is formed for a short time or at a small run, then it is necessary to replace oil scraper caps. Poor quality of gasoline is also possible reason, in this case it is necessary to replace the gas station place.

Fig. 2.12. Wear of electrodes

Candles with the rounded-off electrodes with a small amount of deposits on them and normal color (fig. 2.12) can lead to difficulty of launch of the engine in cold or damp weather and to deterioration in fuel profitability. It is necessary to replace candles on new with the same characteristics.

Fig. 2.13. Cracking or chips of the insulator

Cracking or chips of the insulator (fig. 2.13) demonstrates detonation combustion of fuel. Splinters of the insulator can become the reason of damage of the piston. It is necessary to replace candles; to be convinced of use of fuel with the required octane number; to adjust the ignition moment.

Fig. 2.14. A deposit on the insulator

The deposit sticks to the insulator of a candle (fig. 2.14) , coming off the bottom of the piston or a wall of the combustion chamber with a high frequency of rotation of a bent shaft. It is necessary to clear candles or to replace them with new.

Fig. 2.15. Mechanical damages of a spark plug

Mechanical damages of a candle (fig. 2.15) can be caused by the alien objects which got to the combustion chamber. It leads to destruction of a candle, shutdown of the cylinder and damage of the piston. It is necessary to remove an alien subject from the cylinder and (or) to replace a candle.

Before repeated installation of a spark plug clear a carving and check an integrity of all threads of a carving. At installation you watch lack of a distortion of a candle. For simplification of installation insert a candle into a scrap of a rubber hose and screw it on several turns for the end of a hose. Then tighten a candle key. Moment of an inhaling of spark plugs of 25 N · m.

The description of other works performed at maintenance of the car can be found in appropriate sections.

Spark plugs