4.3. Check of the engine by means of the vacuum gage
Versions of indications of the vacuum gage at diagnostics of malfunctions of the engine
- Using the vacuum gage, it is possible to obtain information on a condition of the engine and to define that laying of a head of the block of cylinders is punched, the power supply system, piston rings or valves is damaged, the system of injection of fuel, etc. is incorrectly adjusted. Unfortunately, indications of the vacuum gage can be interpreted incorrectly therefore these measurements should be used in combination with other methods of check of the engine. Both absolute value of indications of the vacuum gage, and speed of their change are important for the correct definition.
- Connect the vacuum gage to the inlet pipeline. Start and warm up the engine up to the normal working temperature.
- Consider indications of the vacuum gage.
- If the engine is in the normal state, indications of the vacuum gage have to be constants and make 430 ÷ 560 mm of mercury.
Low constant indications of the vacuum gage confirm damage of laying between the inlet pipeline and the case of a throttle, damage of a vacuum hose, incorrectly determined moment of ignition or incorrectly established gas distribution phases.
- If indications of the vacuum gage are lower than norm on 80 ÷ 200 mm of mercury. also fluctuate, perhaps, laying of the inlet pipeline near an entrance opening is damaged or the injector is faulty.
- If indications constantly fall on 50 ÷ 100 mm of mercury. rather stable value, perhaps, valves are damaged. In this case it is necessary to measure a compression in engine cylinders (see the Section Check of Compression Pressure).
- If indications fall, but is not regular, then, perhaps, gets jammed the valve or there is a failure in ignition.
- If at constant turns of idling of the indication quickly fluctuate with an amplitude about 100 mm of mercury., and from an exhaust pipe there is a smoke, perhaps, the directing plugs of valves are damaged.
- If indications quickly fluctuate at increase in turns of idling, then, perhaps, laying of the inlet pipeline or laying of a head of the block of cylinders is damaged, springs of valves are weakened, burned valves or there is a failure in ignition.
Small fluctuations about 25 mm of mercury. are usually connected with failures in system of ignition.
- If indications strongly fluctuate, then, perhaps, laying of a head of the block of cylinders or the cylinder is damaged.
- If the arrow slowly moves over a wide range of values, then, perhaps, the system of the operated ventilation of a case is littered, laying of the inlet pipeline or laying between the case of a butterfly valve and the pipeline is damaged.
- Check, indications of the vacuum gage after sharp and full opening of a butterfly valve and its reset are how fast restored. If the engine is in the normal state, indications reduce almost to zero, then increase approximately on 130 mm of mercury. higher norms decrease to former values at constant turns of idling also again. If indications are restored slowly and pass through a maximum after closing of a butterfly valve, then, perhaps, piston rings are damaged. If there is a long delay, then, perhaps, the system of release of OG is littered.