2.11. Check of a compression

Check of a compression allows to make the conclusion about a condition of the engine. By results of check it is possible to establish degree of wear of valves or pistons (piston rings), and also need of repair of the engine. For check it is necessary компрессометр which for petrol engines can be bought in autoshops.

Prevention

For the diesel engine it is necessary компрессометр with a big scale of measurement.

Distinction in pressure between separate cylinders should not exceed 3,0 bars (the diesel engine of 5,0 bars). If one or several cylinders have distinction in pressure more than 3,0 bars (the diesel engine of 5,0 bars), then it indicates deficiency of valves, wear of rings of pistons or walls of cylinders. At achievement of extreme wear the engine needs to be touched or replaced.

Engine type
Pressure of a compression, bar
New
Limit of wear
Petrol engine
9 – 12
7,0
Diesel engine
34,0
26,0

Petrol engine

PERFORMANCE ORDER
1. When checking a compression the engine has to have working temperature. Temperature of oil is not less than 30 °C.
2. To switch off ignition.
3. To disconnect the plug from Hall's sensor on the ignition distributor.
4. To take out a safety lock No. 15 of a box of safety locks.
5. To disconnect all candle plugs. For this purpose there are special pincers, for example HAZET 1849. They capture the plug only for a tin sleeve.
6. To blow from dirt compressed air of a niche of spark plugs in a head of the block of cylinders and to turn out all spark plugs a suitable candle key.
7. To scroll several times the engine a starter for removal of products of combustion.
Prevention

The transmission in neutral situation, the emergency brake is tightened.
8. To fix or turn, according to the instruction for application, компрессометр in a cylinder opening for a candle.
9. To squeeze out the accelerator pedal till the end and during all check to hold in this situation. The assistant is for this purpose necessary.
10. To turn the engine approximately on 8 turns until on a kompressometra constant pressure is established.
11. To check consistently all cylinders and to compare indications to the required values.
12. To wrap spark plugs and to connect wires of high voltage.
13. To connect the plug to Hall's sensor.
14. To establish a safety lock No. 15.

Diesel engine

Measurement of a compression

Kompressometr VW-1381

Adapter of VW1323/2A


Heat insulator

PERFORMANCE ORDER
1. To warm up the engine in the movement, up to the temperature of cooling liquid of 80 °C.
2. To disconnect an electric wire from the TNVD fuel supply switch, to insulate and put aside.
3. To clean means of cold cleaning the injecting pipelines and to remove, without changing at the same time their curved form.
4. To remove nozzles (see subsection 2.17.7.5).
5. To turn компрессометр instead of a nozzle, having established at the same time between kompressometry and a head of the block of cylinders an old heat insulator.
Prevention

The specified these pressure are valid only when they are measured kompressometry VW-1381 with an adapter of VW1323/2A. By other devices only the difference can be measured in pressure between separate cylinders (see rice. Measurement of a compression).
6. To scroll the engine approximately on 8 turns, so far instrument reading is not stabilized.
7. To wrap nozzles and to tighten the moment 70 N · m.
Prevention

To replace heat insulators between a head of the block of cylinders and nozzles always. Deepening has to be established up (see rice. Heat insulator).
8. To tighten the injecting pipelines the moment of 25 N · m.
9. To connect a wire to the fuel supply switch.