The most effective and common method of checking the cylinder-piston group is considered to be the diagnosis of motor compression. As a rule, it is performed under 2, however, in some cases, it is made unscheduled. In fact, this check is not able to give an unequivocal response about the malfunction of the cylinder-piston group, but it allows you to detect negative changes in its state, based on which, make a decision on more intensive diagnostics, which implies other equipment and complete or partial disassembly of the motor.

Usually, an unscheduled compression test is produced in such situations:

1. If fuel consumption and engine oil rose.
2. If one of the cylinders turned off and stopped participating in the motor operation.
3. If the engine at one point lost power.

Engine compression that this is what it affects

Compression is the maximum pressure index in the cylinder. It is measured at idle, however, at the same time, the air mixture should not be supplied to the motor. The rotation of the crankshaft is carried out using the starter, the installation of the engine to the rolling stand or scrolling the drive wheel during the transfer is enabled. The device measuring compression is called compressometer.

Compression has its impact on many parameters, the main of which are the launchers of the engine, especially at low temperatures. Initially, this applies to diesel engines, where the temperature and pressure of the end of the compression depends, whether fuel flashes in the cylinder. However, the gasoline motors in the cold state are also sensitive to the change of compression - it has its effect on the evaporation of the fuel, which is only theoretically in the cold start on the road to the cylinder should evaporate. In reality, it enters the cylinder in the form of liquid non-combustible drops.

Reduced compression is capable of increasing the pressure of crankcase gases. In this case, a lot of oil vapor flies through the ventilation system. This is pretty unpleasant, as it grows toxicity and the rate of contamination of the combustion chamber increases sharply. The compression unevenly in cylinders is capable of causing vibrations of the motor, which are especially noticeable with small speeds or idling, which, accordingly, harms engine suspension, transmission and car owner itself. In a word, the role of compression as a diagnostic attribute, which largely characterizes the state of the motor, is large enough.

What compression should be

It turns out that compression in the cylinder depends on the level of its compression, and this dependence is determined by a specific coefficient. It is believed that such a coefficient is 1.2 - 1.3 for gasoline four-stroke engines. In other words, if you know the level of compression of your engine, then find the engine compression will be easy (this information can be seen in the official documentation for the vehicle much more often than information about compression).

Undoubtedly, in practice, these compression officials will differ from the officially declared manufacturer, at least because this compression depends on the procedure of natural wear of the piston group, and than this wear is larger, the compression will be less. However, what is the face when compression is the maximum low and engine elements can be considered overly worn out? It is believed that this criterion is about ten or twelve percent of the level of the coprecination, which is declared the manufacturer or obtained by calculations. In other words, if the documentation of the compression rate is 12 kg / cm ², it is not difficult to calculate that the motor with a compression is considered to be faulty less than 10.56 to 10.8 kg / cm ².

Compressometer, instrument for measuring compression, types of compressometers

To check the compression, you will need a compressometer - this device is not expensive and is a manometer having a check valve, with which it fixes the maximum compression in the cylinder. There are such compressometers on constructive execution:

1. With a threaded tip, which screws up instead of a candle.
   
2. With a conventional rubber tip that you need to insert the candle to the hole and hold at the time of the check.
   

Preparatory work, what needs to be done before checking engine compression

Before measuring compression in motor cylinders, such conditions should be performed:

1. To get real indicators, you need to charge a battery well, and the starter must turn the motor with a frequency of at least 200 revolutions per minute.
2. Before the start of measurement of the compression, you need to warm up the motor to the operating temperature of 90 elders.

Engine compression, compression check, work stages

1. First of all, you should remove all the candle wires.
2. Then you need to unscrew all the candles, remembering which candle from what cylinder. Some car owners unscrew only one candle in the cylinder in which the compression is currently carried out. However, this is an incorrect idea of \u200b\u200bthe measurement, since eventually erroneous, indexes of compression will be obtained.
   
3. Next, you need to disconnect low-voltage wires from coils, as they can be poured.
4. After that, it is necessary to prevent fuel to cylinders. In the presence of a mechanical fuel pump, disconnect the fuel hose. If the pump is electrical, remove the power wires from all the nozzles, pull out the fuse or the pump relay.
5. In the presence of a compressometer with a rubber tip, you need to insert it into the candle hole and grip tightly. Your assistant must get behind the wheel and open the throttle, squeezing the gas pedal. Then he should rotate the engine with the stoker until the readings on the device will stop growing.
   
6. The readings in this cylinder should be recorded, after which we reset the information on the instrument and carry out this procedure in the remaining cylinders.
7. After measuring compression in the motor, you must collect everything back.

Analysis of the data obtained

On your motor excellent compression, if:

1. Compression in the cylinders is about 11 - 15.
2. The pressure difference between the cylinders is not more than one.

To more accurately determine the limits of the compression rate for a particular motor, pay attention to the technical documents of your vehicle.

If the pressure in some cylinders is an order of magnitude lower, then certain malfunctions exist. To pre-reveal the breakdown in the cylinder, add ten milliliters of pure engine oil to it and make me out again.

If the compression has risen or exceeded the testimony in other cylinders, this indicates a strong wear or rings.

If the compression has not changed, there may be a problem in a loose fit of the exhaust or inlet valve, the crack in the piston, block or head, the test of the cylinder gasket.

Tips of professionals

It is not necessary to make final conclusions, based only on the measurement of compression. Pay attention to many other, equally important factors.