Compression

Compression indicates the status of the engine. Upon ignition of the fuel-air mixture in the combustion chamber there is a very high pressure. This causes large loads on the piston rings, cylinder walls and on the valve and seat. Damage to the head gasket increases the flow of oil and fuel, the bad and the exhaust, respectively, fuming, a drop in power, difficulty in starting a cold engine.

The nominal value of compression

The compression size is different for different types of engines. Normally, when the motor is warm it is from 26 to 32 bar, at least - 18 bar.

The difference must not exceed 3 bar. If the amount of compression is characterized by more than 3 bar, for different cylinders, the reason for this is found in the following:

1. Wear of the pistons or piston rings.

2. Sticking piston rings.

3. Wear cylinder (often a consequence of sticking piston rings).

4. Nagar on the valves and seats.

5. A damaged valve.

6. Burned valve (when the gap is too small).

Measurement of compression

You can independently measure the compression in the presence of compression tester. You need assistant who will scroll engine, while you make measurements. To accurately measure the compression valve mechanism must be adjusted. In the workshop there is a unit of measurement of loss of pressure. With it you can find the item, which is responsible for the pressure loss.

1. Warm up the engine to operating temperature.

2. Lift the hood.

3. Remove the suction line pipe (Fig. 4.22).

4. Remove the nozzles.

5. Remove the nozzle.

6. Set the parking brake and gearshift lever - in the neutral position.

7. Do not crank the engine with the ignition key, or else the engine will be supplied fuel, which may cause damage to the measuring instrument. Use recording compressometer having a contact switch, with which the motor is connected electrically.

8. Screw Compression screw in the appropriate part of the prechamber (Fig. 4.23).

9. Remove the cover of the control unit, disconnect the contact "50" and connect compression gauge.

10. Remove the cap from the "+" on the left inside the arch of the engine compartment.

11. Connect the connector cable compression tester to the "+" (pin "30").

12. Have an assistant press on the accelerator pedal up to the stop and keep it depressed throughout the measurement.

13. Turn the engine starter by pressing the contact switch compression tester (about 5 seconds).

14. Connect the compression gauge to the next cylinder.

15. Check one by one all cylinders and compare the recorded value with the nominal values.

1. drip a small amount of oil in the nozzle orifice, and then again measure the compression.

2. If the value is too low, it may be an indication that the damaged valves, valve seats, valve channels, cylinder head or cylinder head gasket.

3. If you get the best results, the reason should be sought in the piston rings or cylinders themselves. Oil briefly improves sealing piston and cylinder wall, and therefore the compressed air escapes from the high resistance (compared with the previous one).

If the motor is observed leaking compressed air in the area of the engine compartment, the reasons may be the following:

1. The inlet conduit or damper: faulty inlet valve.

2. When you open the radiator or expansion tank: faulty cylinder head gasket, cracked cylinder head.

3. When you open the oil filler neck or taken out the dipstick: worn cylinder walls, pistons and piston rings.

4. "Shots" in the muffler: defective exhaust valve.

Test pressure loss

At the workshop, along with compression often check the pressure loss. To conduct measurements, the engine must be warmed up, all the nozzles - are turned, and the cover of the suction line, oil filler cap and radiator cap - open. To measure the piston cylinder must be inspected at TDC. The tester is connected to the jack of the corresponding cylinder injector and the compressor. Manometer scale was calibrated, before the air is fed into the combustion chamber. If the combustion chamber is the pressure loss, it is shown as a percentage on the instrument dial. The total pressure drop must not exceed 25%, and on the valves and cylinder head gasket, the loss should not be less than 10%, and the piston rings - 20%. Listening to it can be established beyond any air through the suction pipe (delivery pipe) exhaust manifold cover the Gulf oil cooling system through the camera or the adjacent cylinder.