Electronic fuel injection control system (Mercedes-Benz Vito W638)

The engine uses a direct diesel injection system CDI (see figure 5.52). Fuel from the fuel tank is supplied through the fuel filter 2 by the fuel pump 4, which is driven directly from the camshaft. Fuel under pressure of approximately 2 bar flows through shut-off valve Y75 to high-pressure fuel pump 5.



Part of the fuel flow passes through the high-pressure fuel pump restrictor and through the pressure control valve in the distributor Y74. Then the flow through the fuel temperature sensor VZO passes into the heating valve 3. Then the fuel through the fuel filter 2 goes either back to the fuel pump 4 or to the fuel tank 1.

The other part of the fuel fills the pumping space of the high-pressure fuel pump 5. From there the fuel in compressed form (up to 1350 bar) is fed to the distributor. The fuel pressure sensor in the distributor B66 is located in the distributor to determine the operating pressure. The Y74 distributor pressure control valve monitors the fuel flow pressure, and if it is higher, some of the fuel is directed to the fuel return line. The fuel flow from the distributor is fed to the electromagnetic injectors Y20-Y23, which are controlled directly by the engine control unit. Fuel that was not injected into the cylinders, together with fuel leaks through the needle valve and the control plunger, drains into fuel tank 1.