Determination of compression in the cylinders

Compression (pressure in the cylinder at the end of the compression stroke) characterizes the state of the cylinder group (CPG). With proper nutrition and ignition systems by decreasing the power of the engine perform its checks.

To check the engine compression is necessary to warm up to operating temperature, oil level should be normal and the battery must be charged.

On engines with fuel injection system before checking the fuse, remove the fuel pump from the mounting block of the relay and fuse. Then, start up the engine and wait for it to stop.

Compression is determined in the following order:

- Remove the end of high-voltage wires from spark plugs;

- Remove the spark plug;

- Place the rubber tip of the compression tester to the spark plug hole of the first cylinder;

- Press the accelerator pedal all the way and turn the crankshaft starter at 10-15 rpm (Assistant performs), the watch for indications of compression tester;

- Secure the highest value of pressure;

- Repeat for the remaining cylinders.

If the state of CPG is normal, the pressure will increase rapidly.

The minimum allowable pressure in the cylinder, MPa (kgf / cm2):

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

other engines 0.75 (7.35).

The difference in pressure readings between cylinders should not be more than 0.07-0.1 MPa. When one compression cylinder is substantially lower than in the other, then there is a leak of air through the valve in it.

Low pressure in the first cylinder compression stroke, and then its subsequent gradual increase indicate wear of the piston rings. Low compression during the time measurement indicates air leakage through the valves or "burn-out" cylinder head gasket. The leakage through the valve may be caused by it is not properly closed because of soot on his rod and plate, bending the rod, "burning" or saddle valve plates.

To determine the cause of a lack of compression in the cylinder, add approximately 20 cm3 of fresh engine oil through the spark plug hole, and then repeat the test. If the pressure increases, this indicates the wear of piston rings if the pressure does not increase - about leaks from valves or "burning" cylinder head gasket.

If two adjacent cylinders have the same low pressures, most likely that the cylinder head gasket in between "burnt". This is confirmed by the appearance of the coolant in the combustion chamber or engine oil dipstick.

After checking, set the spark plug, connect it to the high-voltage wires and install the fuel pump fuse.