5.4. Check of a compression in cylinders

Compression (pressure at the end of a compression step) in cylinders — the major indicator for diagnostics of a condition of the engine without its dismantling. And on a difference of values in separate cylinders it is possible to determine by its average value quite precisely degree of the general wear of details of conrod and piston group of the engine, and also to reveal malfunctions of this group and details of the valvate mechanism.
Check a compression the special device — kompressometry which can be got freely in large shops of auto parts now.

Note
So looks компрессометр. There are also other options of kompressometr at which instead of the carving union for a vvorachivaniye instead of a spark plug the rubber tip is established. Such kompressometra when checking a compression need to be pressed to a candle opening strongly.

Prevention
Important condition of correctness of indications when checking a compression is serviceability of a starter and its electric chains, and also full state of charge of the rechargeable battery.

You will need a face key "on 21" for a reversing of spark plugs.
1. Launch the engine and warm up it up to the working temperature.
2. Stop the engine, disconnect a block of a plait of low-voltage wires from the ignition module.

Prevention
Provorachivaniye of the engine a starter at the disconnected tips of high-voltage wires and not switched-off module of ignition can lead to breakdown of its high-voltage chain.

3. Turn out all candles (see. "Replacement and service of spark plugs").
4. Switch-off the fuel pump, having removed a block of wires from conclusions of the relay of the fuel pump.
5. Screw in a candle opening of the checked cylinder компрессометр.
6. Press an accelerator pedal against the stop completely to open a butterfly valve.
7. Include a starter and turn it a bent shaft of the engine until pressure in the cylinder does not cease to increase. It corresponds approximately
to four steps of compression.
8. Having written down indications of a kompressometr, establish it to the shooter on zero, having pressed the valve of production of air.

Note
At kompressometr of other design of the indication can be dumped in other ways (according to the instruction to the device).

9. Repeat operations 5-8 for other cylinders. Pressure has to be not lower than 660 kPa (6,65 kgfs/cm2) and more than on 98 kPa (1 kgf/cm2) should not differ in different cylinders. The lowered compression in separate cylinders can result from leaky landing of valves in saddles, damages of laying of a head of the block of cylinders, breakages or burnings of piston rings. The lowered compression in all cylinders indicates wear of piston rings.
10. For clarification of the reasons of an insufficient compression fill in in the cylinder with the lowered compression about 20 cm3 of pure engine oil and again measure a compression. If indications of a kompressometr raised, malfunction of piston rings is most probable. If the compression remained invariable, then it indicates a leaky prileganiye of plates of valves to their saddles or damage of laying of a head of the block of cylinders.

Good advice
The reason of an insufficient compression can be found out also supply of compressed air in the cylinder in which the piston is previously installed in compression step VMT. For this purpose remove a tip from a kompressometr and attach to it a compressor hose. Insert a tip into a candle opening and give to the cylinder air under pressure of 200–300 kPa. In order that the bent shaft of the engine was not turned, include the highest transfer and slow down the car the parking brake. An exit (leak) of air through throttle knot testifies to leakage of the inlet valve, and via the muffler — to leakage of the final valve. At damage of laying of a head of the block of cylinders air will come out through a mouth of a broad tank in the form of bubbles or in the next cylinder that is found on the characteristic hissing sound, and at development of compression rings air will come out via the oil probe.