Operation5562−1/A1
Winterthur Gas & Diesel Ltd.
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1.3 Emergency Operation
If the fuel pressure control system becomes defective, the PCV will control the
pressure in the system when:
D There are missing or incorrect control signals
D A flow control valve of a fuel pump is unserviceable.
When no control signal is received, the fuel pumps are set to the maximum supply
position.
If the fuel pressure is more than the specified pressure (approximately 1050 bar), the
PCV will open to gradually drain sufficient fuel to keep the adjusted maximum
pressure. If this occurs, longer engine operation time must be prevented.
The PCV must be replaced after a longer operation time during emergency operation.
CAUTION
Damage Hazard: Always do a check of the PCV operation
pressure after emergency operation (e.g. no fuel pump control
when the PCV is used for pressure control in the fuel rail).
Damage can occur if the operation pressure is incorrect.
Note: When the PCV opens, fuel will drain and you can hear a loud noise like a
whistle.
2. Functions
2.1 Control Function
The PCV (1, Fig. 1) has a primary piston. A pressure balance between the high
pressure side and the control side of the PCV controls this primary piston. When the
pressure decreases on the control side through a small orifice in the primary piston
(because of the control valve or the pneumatic actuator), the pressure difference
causes the primary piston to move. The PCV then releases fuel through the return
bore.
2.2 Supply Function
During engine stand-by the PCV (1) will open automatically to supply fuel through the
fuel pumps, the HP fuel pipes and fuel rail (4) to keep the fuel warm. Downstream
from the PCV, fuel is collected in the fuel return pipe (7) and flows back to the booster
circuit at 4.0 bar (see also Fuel System 8019-1).
2.3 Emergency Stop Function
If the control valve (2) is energized, the fuel pressure in the fuel rail is immediately
released.
2014
Pressure Control Valve
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