3.4.9. Check of a compression in cylinders of engines

The compression measuring instrument for petrol engines

Check of a compression in cylinders of petrol engines
1. Warm up the engine up to the normal working temperature.
2. Turn out candles.
3. Disconnect a high-voltage wire from the ignition coil.
4. Completely open a butterfly valve.
5. Screw in an opening for a candle of the 1st cylinder the compression measuring instrument.
6. Ask the assistant to press a pedal of a butterfly valve and to include a starter (on carburetor and injector engines). The starter has to join two-three times for a short time.
7. Define the indication of the manometer at the end of each inclusion of a starter and write down the maximum indication. Repeat the procedure for each cylinder. Values of a compression in cylinders have to be 10,3–11,7 atm (limit 7,2 atm). Values of a compression in hotel cylinders should not differ more than for 10%.
8. If the compression is lower than norm, then fill in in the cylinder about 1 tablespoon of oil for the engine and repeat measurements. If the compression increased, then it indicates wear or breakage of piston rings, or the increased wear of walls of the cylinder. If pressure did not change, then the leaky prileganiye of valves to saddles (repair of the valvate mechanism is required), or damage of laying of a head of the block of cylinders near the cylinder is the reason. If low value of a compression in two next cylinders which does not change at oil addition is observed, then laying of a head of cylinders is damaged.

The compression measuring instrument for diesels

The procedure of check differs in nothing from described above, but has the features.

Measurement of a compression on diesel engines
1. For diesels it is necessary to use the special measuring instrument of a compression calculated on much more high pressure.
2. It is necessary to remove from all cylinders tubes and nozzles with ring laying.
3. Track that the valve for drain of air on the measuring instrument of a compression was closed.
4. At installation of nozzles replace ring laying.