5.3. Compression check 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 dismantling. And on a difference of values in separate cylinders it is possible with sufficient degree of accuracy to determine by its average value degree of the general wear of details of shatunno-piston group of the engine, to reveal malfunctions of this group and details of the klapanny mechanism.

Check a compression the special device — kompressometry which can be got now freely in large shops of auto parts.

Note So looks компрессометр, used for an illustration of this book. There are options компрессометров at which instead of the carving union for a vvorachivaniye instead of a spark plug the rubber tip is established. Such компрессометры at compression check simply strongly press to a candle opening.

Prevention Important condition of correctness of indications at check of a compression is serviceability of a starter and its electric chains, and also a full zaryazhennost of the storage battery.

1. Start up the engine and warm up it to working temperature.

2. Reduce pressure in a power supply system (see. «Fuel pressure decrease in a power supply system»). After pressure decrease a safety lock of the fuel pump into place do not establish to disconnect the fuel pump.

3. Remove tips of wires from spark plugs...	4.... also turn out all candles.

5. Disconnect a block of a plait of low-voltage wires from the ignition coil, having disconnected thereby ignition system.

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

6. Screw компрессометр in a candle opening of the checked cylinder.

7. Press an accelerator pedal against the stop completely to open a butterfly valve.

Note For obtaining the correct indications компрессометра the cranked shaft should rotate with frequency of 180-200 mines-1 or above, but no more than 350 mines-1.

8. Include a starter and turn them a cranked shaft of the engine until pressure in the cylinder will not cease to increase. It corresponds to about four steps of compression.

9. Having written down indications компрессометра, establish it to an arrow on a zero, having pressed the valve of production of air.

10. Repeat operations 6-9 for other cylinders. Pressure should be not lower than 1,0 MPas and should not differ in different cylinders more than on 0,1 MPas. 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.

11. For clarification of the reasons of an insufficient compression fill in in the cylinder with the lowered compression about 20 ml of pure engine oil and again measure a compression. If indications компрессометра raised, malfunction of piston rings is most probable. If value of a compression remained invariable, means, plates of valves leaky adjoin to saddles or laying of a head of the block of cylinders is damaged.