How to check compression


Depending on the available compressometer, an assistant may be required. A compression gauge screwed into the hole instead of a candle allows one person to take measurements. Before starting the measurements, you must perform the following preparatory steps:



  • warm up the engine to antifreeze operating temperature (80-90 degrees);

  • disconnect the low-voltage power supply from the ignition coil (do not pull the central wire out of the coil - this can lead to its breakdown during compression measurements);

  • disconnect the supply hose from the gas tank to the fuel pump (to exclude the flow of fuel into the carburetor and engine cylinders);

  • remove the plug from the first cylinder and insert a compression gauge into the hole (screw in);

  • fully open the choke in the carburetor by pressing the gas pedal fully;

  • turn on the ignition and rotate the engine with a starter for 4-5 seconds;

  • record the recorded maximum value of the compressometer;

  • check the compression alternately in the remaining cylinders of the engine.


The working pressure in the cylinders of a gasoline engine must be at least 10 kgf / cm2 (1 MPa). The difference in compression between the cylinders should not exceed 1 kgf / cm2 (0.1 MPa). If the readings obtained are lower than the specified value, then it is necessary to look for the cause that caused the drop in the compression.
You can also check the compression yourself to adjust the possible gaps between the valves. The adjustment method is well known to motorists, so it will not cause difficulties.