All engines
Compression check allows you to draw a conclusion about the condition of the engine. Namely, when checking, you can determine whether the valves and pistons are in order (piston rings), or they are worn out. In addition, the test results indicate that the engine needs repair. To check, you need a compression gauge, which for gasoline engines can be purchased inexpensively from the company's network.
The pressure difference between the individual cylinders can be up to a maximum of 2.0 bar. If the pressure in one or more cylinders differs by more than 2.0 bar, this is a sign of faulty valves, worn piston rings or cylinder mirrors. If the wear limit is reached, the engine must be repaired or replaced.
Engine designations | Compression to bar | |
new | wear limit | |
E1, E3, E5 | 14 | 10 |
VZ, VZE, V5, V6E | 14 | 10 |
AT 6 | 11 | 8 |
BP (SOHC) | 12 | 9 |
BP (DOHC) without catalyst | 14 | 10 |
BP (DOHC) with catalyst | 13 | 9 |
PN (diesel) | 30 | 27 |
1. To check the compression, the engine temperature must be at least +30°C. Then the oil filter is at hand temperature. The engine temperature must not be too high, otherwise the threads in the cylinder head may be damaged when the spark plugs are removed.
2. Turn off the ignition.
3. Gas engine: Disconnect the plug from terminal 15 on the ignition distributor.
4. Diesel engine: Disconnect the plug from the fuel cut-off valve.
Attention! If the plug is not disconnected, fuel will flow out when the crankshaft is turned.
5. Gas engine: Disconnect all spark plug tips. Special tongs are available for this, e.g. HAZET 1849.
6. Blow out the spark plug niches in the cylinder head with compressed air and unscrew the spark plugs with a spark plug wrench.
7. Diesel engine: Remove the injectors and shut off the fuel return line to the injection pump (high pressure fuel pump), see chapter diesel engine.
8. Turn the crankshaft several times with the starter to remove the remaining soot.
Attention! Place transmission in neutral position, apply handbrake.
9. Insert or screw the compression gauge into the spark plug hole as instructed.
10. Ask an assistant to fully depress the gas pedal and hold during the entire test.
11. Let the crankshaft rotate 8 revolutions until the gauge no longer shows an increase in pressure.
12. Check all cylinders and compare with the required value.
13. Gas engine: Screw in the spark plugs and connect the cables, see chapter Maintenance.
14. Diesel engine: Install injectors, see chapter diesel engine.
15. Gas engine: Connect plug to terminal 15.
16. Diesel engine: Connect the plug to the fuel cut-off valve.