New Holland 667TA/EBF, Repair Manual

Page: 69 / 150

2-51
87519804 NA Issued 11-06 Bur
CHAPTER 2 - 667TA ENGINE OVERHAUL
ENGINE REPAIR MANUAL
COMMON RAIL PRESSURE RELIEF VALVE
BS06K067 Figure 2-66
COMMON RAIL PRESSURE RELIEF VALVE
The common rail pressure relief valve is installed at
one end of the common rail, it is designed to protect
the systems components in case of excessive
increase of pressure buildup.
The valve can be single stage (as the ones shown
above) or two stage with two working limits for
pressure relief 1750 bar and 800 bar (25381 psi. and
11603 psi.).
In the second case, when the pressure within the
high pressure system reaches 1750 bar (25381 psi.),
the valve is activated as a single stage one to
exhaust the fuel and consequently reduce the
pressure until reaching the proper pressure. Then it
reduces the pressure into the common rail to
approximately 800 bar (11603 psi.).
The relief valve enables engine operation at limited
p e r fo r m a n c e, avo i d i n g f u e l ove r h e a t i n g a n d
safeguarding the system
If the dual stage relief valve opening pressure is
reached, the EDC7UC31 control unit stops operation
of the pressure regulator. The high pressure pump
will then operate at maximum delivery to the common
rail, and a failure code will be stored.
1. DIRECT TANK DISCHARGE 3. BODY 5. SMALL PISTON
2. STOP 4. SPRING 6. SEAT ON RAIL
A. NORMALLY, THE TAPERED PISTON (5) END STAYS CLOSED THE
DISCHARGE IS DIVERTED TO THE FUEL TANK.
B. IF 1750 BAR FUEL PRESSURE IS EXCEEDED IN THE RAIL, THE SMALL
PISTON MOVES AND THE EXCESS PRESSURE IS DISCHARGED INTO
THE FUEL TANK.
A
4
2
5
3
4
2
5
3
1
6
1
6
B