3.3.1. Diagnostics of a condition of the engine on appearance of spark plugs

1. Normal candle.
Brown or grayish-yellow color and small wear of electrodes. Exact compliance of thermal value of a candle for the engine and operating conditions.

Good advice
When replacing candles on new establish candles with the same characteristics from among recommended by manufacturer.

2. Soot deposits.
Adjournment of a dry soot indicates rich fuel-air mix or late ignition. Causes admissions of ignition, the complicated launch of the engine and unstable operation of the engine. Check whether the air filter is hammered, whether sensors of temperature of cooling liquid and the arriving air are serviceable.

Good advice
Use "hotter" candle (the extended insulator with the central electrode).

3. Oil deposits.
Greasy electrodes and insulator of a candle. The reason — hit of oil in the combustion chamber. Oil gets to the combustion chamber through guides of valves or piston rings. Causes the complicated start-up, admissions in operation of the cylinder and twitching of the working engine. Repair of a head of the block of cylinders and piston group of the engine is necessary. Replace spark plugs.
4. Metallic raid.
Deposits on a skirt of the insulator of oxides of iron of brick-red color from anti-detonation ferriferous additives (ferrotsen) to gasoline. Are postponed by an even, dense bed. During the operation of the engine with big loading under the influence of high temperature and pressure in the combustion chamber oxides are restored in the conducting paths of pure iron closing the central electrode on "weight". It causes admissions of ignition and, as a result, falling of engine capacity and the increased fuel consumption. The catalytic converter of the fulfilled gases which is strongly overheating at hit in it the gasoline engine which did not burn down in cylinders can be in addition damaged. The raid is practically not removed mechanically and does not burn out at the long movement with high speed. If such raid appears on new candles after the small run, replace the gas station place.

Good advice
If there is no opportunity at once to replace candles new, try to remove this raid, having shipped for 10 min. a candle skirts of insulators in orthophosphoric acid or rust solvent (contains orthophosphoric acid). After that clear a raid a nonmetallic brush (it is possible an old toothbrush) and wash out candles at first water, and then gasoline.

5. Early ignition.
The melted-off electrodes. The isolation center is white, but it can be polluted because of admissions of a spark and the deposits getting on it from the combustion chamber. Can lead to damage of the engine. It is necessary to check compliance like spark plug, purity of sprays of nozzles and the fuel filter, operation of cooling systems and lubricant.
6. Detonation.
The insulator can be cracked or with chips that can lead to damage of the piston. Make sure that the octane number of gasoline corresponds to demanded.
7. Mechanical damages.
Damages can be caused by the alien objects which got to the combustion chamber, and in case of use of too long candle the piston can hook on its electrodes. It leads to destruction of a candle, shutdown of the cylinder and can damage the piston. Remove an alien subject from the cylinder and (or) replace a candle.