Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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Section II Working Principle of Low Pressure Fuel Line System
I. Composition of low pressure fuel line:
The low pressure fuel line is functioned to supply sufficient fuel to the
high pressure fuel line and is composed of:
z Fuel tank (including filter screen)
z Fuel filter (including manual fuel delivery pump)
z Low pressure fuel delivery pump
z Other low pressure fuel hoses
II. Fuel tank
The fuel tank shall be fabricated from anti-corrosion material and shall maintain 0.3bar pressure under all working
conditions and be free of fuel leakage under the application of the doubled working pressure. The fuel tank shall also
set up appropriate opening or safety valve or adopt appropriate measures to relieve the excessive pressure whenever
it's needed. When the motor vehicle is subject to slight vibration, makes turns or travels or parks on a slope, the fuel in
the fuel tank shall not leak from the fuel tank cap or the pressure balancing device.
III. Fuel filter (including manual fuel delivery pump)
Sunray long-wheelbase model adopts two-stage diesel filter, including
one primary filter and one fine filter. Compared with traditional diesel
engines, it requires cleaner fuel supply. The impurities contained in
the fuel will damage the fuel system including the high pressure pump,
high pressure common rail, and fuel injector. The fuel filter purifies
the fuel inputting into the high pressure fuel pump, in order to help the
normal functioning of the high pressure pump. The contaminant,
impurity, and particle in the fuel will lead to the damage of pump units,
fuel supply valve, and fuel injector. Therefore, the use of fuel filter
capable of meeting the fuel injector requirements becomes the
premise for normal working of the engine and guarantee of service life.
The water content in the diesel may exist in non-free radical form
(emulsified fuel) or radical form (such as water condensate generated
due to variation of temperature). If entering into the fuel injection
system, this water content will lead to damage of parts due to corrosion.
Similar to other fuel injection systems, common rail system requires
the fuel filter with water collection chamber as well as the automatic
water content alarm. When the alarm lamp lights up, make sure to
drain the water from the water collection chamber.
The fuel filter is composed of fuel temperature sensor, fuel heater,
manual fuel pump, fuel-water separator, and water level sensor.
The fuel leakage during traveling or the air ingress into fuel pipeline
after replacement of fuel filter may lead to start failure or poor
functioning of the engine. Therefore, make sure to bleed the air from
the low pressure fuel pipeline after the installation of manual fuel
delivery pump. Installed on the fuel filter, the manual fuel delivery
pump is the device for supplying fuel to the fuel filter and the device
required to guarantee the first start of the engine. In event of the
following conditions, press the manual fuel delivery pump, till the
manual fuel delivery pump can’t be further pressed, before starting the