We carry out the check on the engine warmed up to operating temperature. Relieve pressure in the engine power system (see «Fuel filter replacement») and do not replace the fuel pump fuse. Remove spark plugs from cylinder head (see «Checking the condition and replacing spark plugs»).
Disconnect the engine management wiring harness connector from the ignition coil (see «Removing the ignition coil»).
We install the tip of the compression gauge in the spark plug hole in the cylinder head.
Connect the wire terminal to «negative» battery terminal.
We turn the crankshaft with the starter with the pedal fully depressed «gas» within 2-4 s (the pressure gauge should stop increasing).
We fix the pressure gauge reading and release the pressure in the compression gauge.
For a correct assessment of compression, the battery must be fully charged - the crankshaft revolutions during scrolling must be at least 180 min-1.
Similarly, we check the compression in other cylinders of the engine. The compression of a serviceable engine should be in the range of 11.0-13.0 bar, and the difference in readings between the cylinders should not exceed 1.0 bar. To find out the reasons for low compression, pour 10-15 cm3 of engine oil into the cylinder through the spark plug hole and repeat the measurement. In the event that the compression increased by more than 2.0 bar during the re-measurement, the most likely cause of the malfunction is severe wear, sticking or breakage of the piston rings. If the pressure gauge readings did not increase after filling the oil, then most likely the valve plates do not fit snugly against the cylinder head seats. This can happen if there is a violation of the thermal gaps in the valve drive, as well as with a lot of wear, burnout or damage to the plates or valve seats. It is possible to finally find out the cause of the malfunction only after disassembling the engine.