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Check of the engine by means of the vacuum gauge

Using the vacuum gauge, it is possible to receive the information on a condition of the engine and to elicit the fact of infringement of serviceability of functioning of the power supply system, damage of a lining of a head of cylinders, piston rings, valves and so forth Unfortunately, vacuum gauge indications can be easily incorrectly interpreted, therefore the analysis of the given measurements should be made taking into account the results of checks of the engine which are carried out by other methods.

At check are important both absolute values of indications of the vacuum gauge, and speed of their change.

Substantive provisions and fluctuations of an arrow of the vacuum gauge at diagnostics of malfunctions of the engine


  1. Connect the vacuum gauge to the inlet pipeline. Start the engine and warm up it to normal working temperature.
  2. Consider vacuum gauge indications.
    • If the engine is in a normal state, vacuum gauge indications should be stable and make 430-560 mm Hg
    • Low stable indications of the vacuum gauge can specify in the fact of destruction of a lining between the inlet pipeline and the case of a throttle, damage of a vacuum hose, infringement of installation of the moments ignitions/phases timing.
    • If vacuum gauge indications are astable (arrow fluctuations) take place and are underestimated concerning norm on 80 - 200 mm Hg, it is necessary to check up a condition of a lining of the inlet pipeline near to an entrance aperture. The probability of failure of a corresponding injector is not excluded also.
    • Constant falling of indications on 50 - 100 mm hg concerning stable value in high degree of probability specifies in damage of valves, - measure компрессионное pressure in cylinders.
    • Irregular falling of indications can speak about valve jamming, or failure in ignition.
    • If indications quickly fluctuate with amplitude about 100 mm Hg at stable turns of idling, and on an exit of system of release takes place strong дымообразование, it is necessary to check up a condition of directing plugs of valves.
    • Fast fluctuations of indications at increase in turns of idling, can be the certificate of damage of a lining of the inlet pipeline and-or a head of cylinders, easings клапанных springs of valves, a burn-out of plates of valves, and also failures in ignition.
    • Insignificant fluctuations in a range of 25 mm are hg usually connected with failures in ignition system.
    • If indications strongly fluctuate, probably, damage of a lining of a head of cylinders, or walls actually the cylinder takes place.
    • Slow movement of an arrow in a wide range of values, is told about a contamination by system of operated ventilation картера (PCV), damage of a lining of the inlet pipeline, or a lining between the case throttle заслонки and the pipeline.
  3. Check up, indications of the vacuum gauge after sharp and full opening throttle заслонки and its return to a starting position are how fast restored. If the engine is in a normal state, indications fall almost to zero, then increase approximately on 130 mm Hg above norm and again decrease to former values at stable turns of idling. If indications are restored slowly and pass through a maximum after closing throttle заслонки, probably, piston rings are damaged. The long delay testifies to possible infringement of passableness of system of release.