The main elements of the PVC system
1 - air purifier; 2 - air duct; 3 - ventilation hose; 4 - cylinder head cover; 3 - oil separator, 6 - PVC valve; 7 - ventilation hose; 8 - intake manifold.
Closed-circuit positive crankcase ventilation ensures return of incompletely burned fuel (passing into the crankcase, bypassing the piston rings) back to the intake manifold for re-burning with the air-fuel mixture.
A valve, known as a PVK valve, regulates the flow of air into the manifold in accordance with the degree of vacuum in it. With a sufficiently wide opening of the throttle valves, the specified valve is fully open. However, at idle, at maximum manifold vacuum, the PVK valve reduces the air flow so as not to have an unnecessary effect on the small amount of mixture passing into the engine.
At a fully open throttle, with an increase in the volume of gas entering the crankcase, and with a decrease in the degree of vacuum in the manifold, the inflow through the PVK valve becomes insufficient. Under these conditions, excess vapors are sucked into the air cleaner and enter the engine along with fresh air. A blocked valve or hose can cause rough idle, engine stall or low idle, oil intrusion into the engine and/or sludge and oil deposits in the engine and air cleaner. A leaky valve or hose can cause erratic idle or engine shutdown.
Examination
PVK check is carried out when the engine is idling (after warming up).
Remove the PVC valve from its sleeve without disconnecting it from the hose. (Most valves are pressed into sleeves, however some are threaded and screw into sleeves).
To check for vacuum, place your thumb on the end of the valve stem.
If there is no vacuum, check if the hoses or fittings are clogged. If the nozzles are clean, then the valve is faulty.
With the engine off, remove the PVC valve, shake it, listening to the sound from the needle inside it. No sound indicates that the needle is stuck and the valve needs to be replaced.
If the valve has a thread, it is recommended to use a thin wire that is inserted into the valve (1) on the threaded side to check plunger movement. If no movement is felt, the valve must be replaced.
CAUTION: An engine operated without crankcase ventilation can quickly fail. It is important to check and replace the PVC valve at regular intervals.
Removal and installation
Remove the PVC valve from the sleeve. Disconnect the hose from the valve. Note which side of the valve was inserted into the manifold.
Check the hose for cracks, kinks and blockages.
Check nozzle (to which the hose is attached) for blockage.
The normal functioning of the PVC system depends on the tightness of the engine. Check the PVC system in the following cases:
- unstable engine idling, the causes of which cannot be attributed to the usual violation of vacuum or a problem with the fuel supply;
- air infiltration through a leaky valve sleeve, oil sump gaskets, or even front and rear crankcase seals;
- excessive contamination of the air cleaner with low mileage;
- noticeable contamination of the engine oil due to fuel dilution long before the scheduled oil change is due.
WARNING: Engines with severely worn rings and! or valve seals can have gas blow-by so intense that the PVK system cannot cope with it.