The compression (pressure in the cylinder at the end of a compression step) characterizes a condition of tsilindroporshnevy group (TsPG). At serviceable power supply systems and ignitions in case of deceleration of power of the engine carry out its check.

For check of a compression the engine should be warmed up up to the working temperature, the level of oil has to be normal, and the rechargeable battery has to be loaded.

On engines with system of injection of fuel before check remove the fuse of the fuel pump from the assembly block of the relay and safety locks. Then launch the engine and wait for its stop.

The compression is defined in the following order:

– disconnect tips of high-voltage wires from spark plugs;

– turn out spark plugs;

– establish a rubber tip of a kompressometr in an opening of a spark plug of the first cylinder;

– press against the stop a pedal of an accelerator and turn a bent shaft a starter on 10-15 of turns (the assistant carries out), at the same time watch indications of a kompressometr;

– record the highest value of pressure;

– repeat operations for the remained cylinders.

If the condition of TsPG is normal, then pressure will quickly increase.

Minimum admissible pressure in the cylinder, MPa (kgf/cm2):

        RP and AAM 0,70 (6,86) engines

 other       engines 0,75 (7,35).

The difference in indications of pressure between cylinders should not be more than 0,07-0,1 MPas. If in one cylinder the compression is much lower, than in the others, so leak of air via valves in it takes place.

Low pressure in the cylinder on the first step of compression, and then its gradual increase at the subsequent is pointed out wear of piston rings. The low compression during the whole time of measurement demonstrates leak of air via valves or "burn-out" of laying of a head of the block of cylinders. Leak via the valve can be caused it by leaky closing because of a deposit on its rod and a plate, a bend of a rod, "burn-out" of a saddle or a plate of the valve.

For establishment of the reason of an insufficient compression add to the cylinder about 20 cm3 of fresh engine oil through an opening for a spark plug, and then repeat test. If pressure increases, then it testifies to wear of piston rings if pressure does not increase — about leaks via valves or "burn-out" of laying of a head of the block of cylinders.

If two adjacent cylinders have equally low values of pressure, it is the most probable that laying of a head of the block of cylinders between them "burned through". It confirms also emergence of cooling liquid in combustion chambers or on the index of level of engine oil.

After check establish spark plugs, connect to them high-voltage wires and establish a safety lock of the fuel pump.