Fuel Tank: Description and Operation

Fuel Supply, Low-pressure Side


Fuel tank







Depending on the engine variant, a fuel tank with a filling capacity of 22.4 gal. (85 l) or 26.4 gal. (100 l) is installed. The tank bladder is identical. In the fuel tank with a filling capacity of 22.4 gal. (85 l), the roll-over valve is positioned lower down in the fuel tank by way of an adapter, with the result that the fuel nozzle is then switched off earlier.

- Cayenne V6/Cayenne S - filling quantity 22.4 gal. (85 l), reserve 3.9 gal. (15 l)
- Cayenne Turbo - filling quantity 26.4 gal. (100 l), reserve 3.9 gal. (15 l) (option for V6/S)

The active carbon filter is located behind the wheel housing liner of the right rear wheel. On USA vehicles, a leak detection pump (LDP) is used for the tank leakage test, as previously in the Cayenne vehicles. This pump is installed directly at the fresh-air connection of the active carbon filter.

ReturnLess Fuel System - RLFS

The low-pressure side of the fuel supply system consists of a returnless fuel system (RLFS - ReturnLess Fuel System). The speed-regulated electric fuel pump delivers the fuel via the fuel filter and fuel-pressure regulator (in the fuel tank) to the quantity control valve on the high-pressure pump with a pressure of approx. 82 psi (5.7 bar). The sucking jet pumps in the fuel tank are also operated with the low-pressure side. The 2 fuel-level sensors are installed in the fuel tank for measurement of the fuel level.

1 demand-controlled electric fuel pump as well as the fuel filter (lifetime filter) and the fuel-pressure regulator (rel. fuel pressure approx. 82 psi/5.7 bar) are located in the fuel tank.


(4 bar).

Internal design of the fuel tank RLFS







NOTE:
- The procedures for checking the fuel pressure, holding pressure and delivery rate of the electric fuel pump are described in the PIWIS information system.
- The safety instructions in the PIWIS information system must be observed when working on the fuel system.

Fuel tank ventilation

Tank ventilation










The fuel tank is aerated and vented exclusively via the active carbon filter, which acts as an intermediate storage device for any HC emissions. Regeneration of the active carbon filter takes place via the tank vent valve when the engine is running.

The active carbon filter is installed behind the wheel housing liner at the rear right. The tank vent valve is located in the engine compartment (on the right next to the electronic throttle in V8 engines).

When the engine is running, the fuel tank is vented by the tank vent valve, which is controlled by the DME control unit, to the intake system of the engine.
- On the turbo engine, a check valve closes the connection to the intake manifold when boost pressure is present.

Leak detection pump (LDP), for USA vehicles only

The functional principle for tank leakage diagnosis (LDP) is identical to that of the previous Cayenne vehicles. The complete fuel tank system is checked for possible leaks using the positive pressure method. This takes place only when the engine is running. The LDP is an electro-pneumatic diaphragm pump which is supplied with a vacuum. Evaluation by means of a reed contact switch located on the diaphragm takes place after the pumping phase.