Engine
SHOP MANUAL
Ch 1 page 19
Route of the fuel on 9 and 13 litre engines
The feed pump draws fuel from the fuel tank. The fuel is taken into connection 1 and drawn through the suction
filter. From the suction filter the fuel is drawn into the control unit cooler via the fuel hose 2 and then from the
control unit cooler to the feed pump via the fuel hose 3.
The feed pump builds up the fuel pressure to between 9 and 12 bar and forces the fuel through the pressure
filter via the fuel pipe 4. The fuel flows from the pressure filter via the fuel pipe 5 on to the fuel inlet metering
valve fitted on the high pressure pump.
The fuel inlet metering valve controls how much fuel should be led into the high pressure pump when
requested to do so by the engine control unit.
The high pressure pump builds up the fuel pressure to a maximum of 3,000 bar. The fuel is taken on to the
accumulator via high pressure pipe 7.
A high pressure pipe 8 runs from the accumulator to each connection bringing fuel to the injectors. When the
solenoid valve in the injector is supplied with voltage, the injector opens and fuel is injected into the cylinder.
The fuel system works under high fuel pressure and it is therefore important that there is no water in the fuel.
Water causes corrosion of the fuel system components and the components will be damaged due to the sys-
tem’s tight tolerances. To prevent water from being present in the fuel, water is separated from the fuel at the
suction filter and taken back to the fuel tank via the pipe 6.
There is a safety valve 9 on the accumulator that opens if there is a fault in the fuel system, which results in the
fuel pressure becoming too high. The safety valve opens at a pressure of 3,000 bar and reduces the fuel
pressure to 1,000 bar and then regulates the fuel pressure so that it remains at 1,000 ± 300 bar. When the
safety valve opens, the fuel is returned via the pipe 10. Fuel which is taken out via the safety valve will heat up
the pipe downstream of the safety valve.
Excess fuel from the injectors flows from the fuel manifold back to the fuel tank via the pipe 11.
Figure 29
References in the text refer to
the numbers in figure 29.
Low pressure
High pressure
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