Fuel, Exhaust & Engine Electrics
Page 2.11
Functional diagram of the low pressure side in the fuel tank.
Fuel Pressure On The Low Pressure Side.
For DFI engines, the fuel pressure on the low pressure side has been
increased to approx. 80 psi/5.5 bar (this was previously approx. 58
psi/4 bar). The left or right fuel pump is operated as the main pump in
order to distribute the higher load to both fuel pumps, depending on the
fuel level.
The fuel pumps are activated if the level of fuel in the tank is
reduced and if the engine requires more fuel:
• Fuel level > 15.8 gal. (60 liters) to 26 gal. (100 Iiters): When the tank
is relatively full, the right fuel pump is activated; if more fuel is
required (> 13 gal./50 liters/h), the left pump is activated.
• Fuel level > 4 gals/15 liters to 15.8 gals/60 liters: When the tank is
half-full, the left fuel pump is activated; if more fuel is required (> 13
gals/50 liters/h), the right pump is activated.
• Fuel level < 4 gals./15 liters: If the tank is relatively empty, both
pumps run continuously.
Other switching functions include:
• If the ignition was switched off for more than 30 minutes, the left fuel
pump is activated for approx. 1 to 2 seconds when the driver’s door
is first opened in order to build up fuel pressure even before the igni-
tion is switched on.
• Both fuel pumps are activated while starting the engine and for
several seconds after starting the engine.
T - Tank filler neck
R - Fuel pump unit in right side of tank
L - Fuel pump unit in left side of tank
SL - Sucking jet pump for left fuel pump
SR - Sucking jet pump for right fuel pump
F - Fuel filter (does not need to be changed)
D - Fuel pressure regulator (approx. 80 psi/5.5
bar)
EV - Fuel injectors (cylinders 1 to 6 or 1 to 8)
P - Fuel pressure approx. 80 psi/5.5 bar
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