To removal and installation of spark plugs apply a special candle key. Before removal of spark plugs let's to the engine cool down and clear a niche brush round candles in a head of the block of cylinders. At replacement use only the candles recommended by manufacturer. On petrol engines establish candles of the following brands and their analogs:

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 lateral electrode.

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

The removed candle examine, and then if it is repeatedly established, clear a brush and (or) blow the 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 an engine condition. The candle (fig. 2.4) working in normal conditions, has brown or grayish and yellow color of an insulator and electrodes.

Fig. 2.5. Soot deposits on a spark plug

Adjournment of dry soot (soot) indicates (fig. 2.5) a rich fuel and air mix or late ignition. It leads to the ignition admissions, the complicated start-up and unstable operation of the engine. Thus check and if necessary replace the air filter, check and adjust fuel level in the poplavkovy chamber 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 an insulator are caused by oil hit in the combustion chamber via directing plugs of valves or through piston rings. The complicated start-up of the engine, admissions in operation of the cylinder and twitching of the working engine (its unstable work) is thus observed.

Fig. 2.7. Obgoraniye of spark plug electrodes

The glossy white insulator of the central electrode, the scorched electrodes and absence of deposits (fig. 2.7) are symptoms of an overheat of a candle which reduces its resource. Early ignition, a poor mix, подсос air in the inlet pipeline can be the reasons discrepancy such as a candle, recommended for this engine. The overheat of the engine and, respectively, an overheat of candles can be caused by insufficient level of cooling liquid and a radiator contamination.

Fig. 2.8. Oplavleniye of spark plug electrodes

The melted-off electrodes, white insulator (or polluted by deposits getting on it from the combustion chamber at the ignition admission) (fig. 2.8) testify to early ignition. Thus it is necessary to check compliance such as spark plugs, installation of the moment of ignition, structure of a fuel and air mix, work of systems of cooling and greasing.

Fig. 2.9. Change of color of an 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 current-carrying — it causes admissions in an iskroobrazovaniye on 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 lateral electrodes (fig. 2.11) , lead to isolation of electrodes, cause admissions in an iskroobrazovaniye 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 small run, it is necessary to replace maslosjemny caps. Also possible reason is poor quality of gasoline, in this case it is necessary to replace a filling place.

Fig. 2.12. Wear of electrodes

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

Fig. 2.13. Cracking or insulator chips

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

Fig. 2.14. A deposit on an insulator

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

Fig. 2.15. Mechanical damages of a spark plug

Mechanical damages of a candle (fig. 2.15) can be caused by the alien subjects which have got to the chamber of combustion. It leads to candle destruction, shutdown of the cylinder and piston damage. 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 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 some turns for the hose end. Then tighten a candle key. Moment of an inhaling of spark plugs of 25 N · m.

The description of other works which are carried out at maintenance of the car, it is possible to find in appropriate sections.

Spark plugs