Audi 2003 A8 Technical Features page 38

Engine, Mechanics
Fuel system (hydraulics)
Pressure regulator
(4 bar)
Fuel pump G23
When the ignition is switched on (terminal 15),
the fuel pump G23 conveys a maximum
volume to the pressure regulator at the fuel
rail to achieve short starting times.
The pump G6 also conveys fuel to the
pressure regulator and additionally into the
pipes for the two suction jet pumps in the
side tank compartments.
The suction jet pumps convey the fuel from
the side compartments "diagonally" into the
pump reservoirs.
38
Suction jet pump
Such pipe routing prevents dry running of a
pump in critical driving situations such as
cornering or if the vehicle is at an extreme
angle.
The return pipe is shared by both reservoirs.
If one reservoir is full, the pipe is closed by a
non-return valve and the entire return volume
runs into the second reservoir.
If both reservoirs are full, the non-return
valves are overridden and the fuel runs into
the tank.
Fuel pump G6
SSP282_005