Pic. 7.25. Scheme of forced crankcase ventilation: 1 - PCV valve; 2 - crankcase gases; 3 - fresh air
The forced crankcase ventilation system ensures the suction of crankcase gases and fuel vapors from the crankcase into the engine intake pipeline, as a result of which pressure increase in the crankcase due to the penetration of exhaust gases into it and their release into the atmosphere is excluded (pic. 7.25). The crankcase gases are mixed with fresh air and fed through the forced crankcase ventilation valve to the intake manifold.
The main components of the positive crankcase ventilation system are the valve, filter and vacuum hoses.
To maintain idle speed, the PCV valve limits flow when intake manifold vacuum is high. If the breakthrough of exhaust gases into the engine crankcase is large, for example, when piston rings are worn, the forced crankcase ventilation system directs crankcase gases to the air filter, where they are further burned in the engine cylinders.
Checking the positive crankcase ventilation valve is given in section 2.