Note. Before checking, the engine must be warmed up to normal operating temperature. and the battery must be fully charged.
2. Clean the spark plug seats before removing them, using compressed air and a brush if necessary. On thin horses, you can use a bicycle pump. The purpose of this operation is to prevent dirt from entering the cylinders.
3. Remove spark plugs from all cylinders (see chapter 1).
4. Lock throttle valve fully open.
5. Disconnect the central high voltage wire from the distributor cap and ground it to the cylinder block with a jumper wire "crocodiles" (on models without a distributor, disconnect the electrical connector from the ignition coil unit). De-energize the fuel system pump by pulling the appropriate fuse.
6. Insert the compression gauge into the spark plug hole (pic. 3.6).
7. Turn on the starter and crank the engine for at least seven compression strokes, observing the compression gauge readings. With a good engine, the reading should increase quickly. A slow build-up of pressure indicates worn piston rings. A slight pressure in the first stroke, which does not increase in subsequent strokes, indicates valve leaks. or for a breakdown of the cylinder head gasket. The cause may also be carbon deposits on the valves or a crack in the cylinder head. Record the highest pressure in the cylinder.
8. Repeat check for other cylinders. Compare your results with the values given in "Technical Data" this chapter.
9. Pour some engine oil through the spark plug hole (about a foot spoon) to each cylinder and repeat the test.
10. If the compression increased after filling the oil, then the piston rings are definitely worn out. If the pressure has not changed significantly, then the valves or gasket are leaking. Valve leaks can be caused by burnt, cracked, or warped valves and valve seats.
11. If two adjacent cylinders have the same low compression, this almost certainly means a breakdown of the gasket between them. This can be confirmed by the appearance of coolant in the combustion chamber or in the crankcase.
12. If the pressure in one of the cylinders is slightly lower than in the others, and the engine does not idle quite steadily, the knowledge of the exhaust valve cam may be a possible cause.
13. If the pressure is unusually high, it is possible that the combustion chamber is covered with a thick layer of soot. In this case, the cylinder head must be removed and cleaned.
14. If the pressure drops or differs greatly from cylinder to cylinder, contact a service station to check the engine on diagnostic equipment. Such a check will accurately determine the location of the leak and the severity of the malfunction.