8.5. System of compulsory ventilation of a case

Fig. 8.4. Scheme of system of compulsory ventilation of a case: 1 – the soaking-up branch pipe; 2 – air filter; 3 – spool-type device; 4 – cover of a head of the block of cylinders; 5 – fresh air; 6 – crankcase gases; 7 – fuel-air mix

Compulsory provides to ventilation of a case decrease in the fulfilled gases of content of hydrocarbons due to circulation of fresh air through a case, its mixing with crankcase gases and the directions of this mix in the soaking-up branch pipe for reburning in the combustion chamber of the engine (fig. 8.4).
The system consists generally of vacuum hoses and the spool-type device which provides adjustment of a stream of gases according to the frequency of rotation of a bent shaft of the engine and extent of depression on the soaking-up branch pipe.

Check of technical condition
Operability of system of ventilation of a case can be checked easily.
This system needs to be checked regularly as the zolotnik and vacuum hoses usually get littered with soot and resinous deposits from a stream of gases. At reduction or the termination of a stream through a zolotnik the frequency of rotation of a bent shaft of the engine idling, as a rule, decreases and the engine idles unstably.
For check of depression in system uncover the air filter and find the small filter of system of ventilation of a case which is located from the inside of the case of the air filter.
Disconnect the hose going to this filter.
During the operation of the engine idling close a thumb a hose opening – small depression has to be felt. If gradually to remove a finger, then it is possible to hear hissing. It indicates that air is sucked in on all highway of system. If depression is felt, the system is serviceable. Check purity of the filtering element. If there are suspicions that the filtering element is polluted, replace it as it is inexpensive operation, but the ensuring safety during the operation of the engine.
If on the end of a hose depression weak, so the highway of system is littered and its further check is required.
Switch off ignition, find the spool-type device of system of ventilation and carefully take out it from a rubber cover. Shake a zolotnik and listen to the arising sound like knocks (clicks). Knocks are caused by a zolotnik ball. If knocks arise not at each stirring (knock not free), replace a zolotnik.
Launch the engine and let's it work idling at the removed zolotnik. Close a thumb an opening of a zolotnik and check depression. It has to be considerable and be felt at once.
If depression on a zolotnik weak or is not felt in general, switch off ignition and disconnect a vacuum hose from other end of the valve. Launch the engine and idling check depression on the end of a hose which is disconnected from a zolotnik. Lack of depression indicates pollution in a hose or soaking-up engine branch pipe. If the hose is littered, replace it or remove from the engine and blow compressed air. If channels of the carburetor through passage or the soaking-up branch pipe are littered, it is necessary to remove these units and to carefully wash out them to remove resinous deposits. If depression on a hose without zolotnik strong, and on a zolotnik entrance at the connected hose weak, the zolotnik is faulty – its replacement is necessary.
Getting a new zolotnik of system of ventilation of a case, be convinced that this detail corresponds to type of your engine. Otherwise there can be too weak or too strong depression that can lead to an engine exit out of operation.

Replacement of elements
Operations on replacement of a zolotnik and the filter of a zolotnik see in section 2.