New Generation N62 Engine Chapter 6 P.8
Course Contents/Background Material
© BMW AG, Service Training
- Fuel supply system
The fuel tank system must fulfil various requirements concerned
with supplying the engine with fuel. These include:
- Providing sufficient fuel at each service point
- Ensuring fuel supply regardless of the driving style
- Ensuring that the tank can be almost completely drained
The tank geometry presents an added difficulty. This is due to
the installation location in the vehicle. The tank is made up of
two halves which are only directly connected up to a certain
height.
A large proportion of the fuel volume cannot reach the fuel pump
without technical assistance.
Fuel supply system structure:
- Fuel tank (22)
- Surge chamber (18)
- Fuel pump (19)
- Two suction jet pumps (21)
- Outlet protection valve (23)
- Pressure relief valve (20)
- Internal tank fuel lines
- Fuel filter with fuel pressure regulator (25+26)
- Fuel distributor pipe with injection valves (27)
Internal tank fuel circuit operation
The fuel pump pumps fuel from the surge chamber via the fuel
filter to the injection valves as required. The fuel pump always
pumps more fuel than the engine requires in all operating condi-
tions.
The fuel pressure regulator built into the fuel filter adjusts the
pressure to 3.5 bar and feeds the excess fuel in the return flow
back into the tank. The pressure regulator valve in the return
flow sets a return pressure of 1.0-1.5 bar.
This pressure should prevent fuel vapour locks in the return flow
and should also ensure operation of the two suction jet pumps
(delivery rate required for both pumps = 25 litres per hour) at the
same time.
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