Page 270 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

During acceleration and heavy-load operations when blow-by gases are at their maximum, low vacuum in the
intake manifold allows the springs to keep the plunger “back” for maximum airflow through the PCV valve.
In the case when the intake manifold becomes pressurized, such as during boost on turbocharged engines or
during backfire, the plunger’s seat is forced against the valve case preventing air from entering the crankcase.
Crankcase depression regulator valve (CDRV) for diesel engine
A crankcase depression regulator valve (CDRV) is used to regulate the flow of crankcase gases back into the
engine. This valve is designed to limit vacuum in the crankcase. The gases are drawn from the valve cover
through the CDRV and into the intake manifold.
Fresh air enters (Fig 3) the engine through the combination filter, check valve, and oil fill cap. This air mixes with
blow-by gases and enters the opposite valve cover. These gases pass through a filter on the valve cover and are
drawn into the connected tubing.
Intake manifold vacuum acts against a spring loaded diaphragm to control the flow of crankcase gases. Higher
vacuum levels pull the diaphragm close to the top of the outlet tube. This reduces the amount of gases being
drawn from the crankcase and decreases vacuum in the crankcase. As intake vacuum decreases, the spring
pushes the diaphragm away from the top of the outlet tube allowing more gases into the manifold. The diesel
crankcase ventilation system should be cleaned and inspected every 15,000 miles (24,000 km) or at 12 month
intervals.

Evaporative control system i.e. charcoal canister
Evaporator emission control system
This system accounts for about 20% of the total fuel emissions from the engine. In this, the fuel gets emitted
without being used, hence it is necessary to control evaporative emissions to prevent the fuel from being emitted
and to put it to use.

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CITS : Automotive - Mechanic Diesel - Lesson 80 - 83