Fuel and ignition system 9112 · 20 Non-return flow fuel supply Fuel routing in engine com

Fuel and ignition system 9112 20 Non-return flow fuel supply Fuel routing in engine compartment system (RF) In the non-return flow fuel supply system (Returnless Fuelsystem) the fuel pressure regulator and the fuel filter are integral with the fuel tank. Therefore, the fuel return line from the fuel rail in the engine compart- ment to the fuel tank is not needed. The surplus fuel delivered from the electric fuel pump consequently enters the fuel tank directly from the pressure regulator. Only the fuel quantity injected from the injection valves is delivered to the fuel rail in the engine compartment. Dispensing with the return line has the advantage that no fuel warmed in the engine compartment returns to the fuel tank thereby raising the tem- perature in the fuel tank. This results in a further decrease in hydrocarbon emissions (HC) in the fuel tank and also less strain on the tank ventilation. Tasks such as checking fuel pressure, holding pressure and delivery rate of fuel pump and any special tools requirements are described in the Technical Manual. 2070 Control unit for the demand control of fuel delivery rate (EKPSM) Only Carrera 4 cars for the USA have an additional electronic control unit installed below the fuel tank cover located between the fuel pump relay and the fuel pump. This allows reduction of the fuel pump de- livery rate during low fuel consumption, which also reduces the warming of fuel in the fuel tank. Activation of the electronic 2_06_02 fuel pump control module (EKPSM) through the Motronic ME 7.8 is carried out via an A – Fuel supply (system pressure 3.8 bar) earth switched PWN signal with a frequency 1 – Connection for pressure test of 10 Hz. This realises an engine-speed- dependent, two-stage control. Up to ap- prox. 2000 rpm the delivery rate is reduced to approx. 50 l/h. At a higher engine speed the delivery rate is increased to approx. 80 l/h. 2 - 2 Service Information 2002