Fuel Filter: Description and Operation

GF47.20-P-2110MIK Component Description For The Fuel Filter With Fuel Pressure Regulator
- ENGINE 272.942 in MODEL 171.454 as of Model Year 09 / AEJ 08 model refinement package
- ENGINE 272.969 in MODEL 171.458 as of Model Year 09 / AEJ 08 model refinement package





Sectional view of fuel tank
55/2 Fuel filter with fuel pressure regulator
75 Fuel tank
B4/3 Tank pressure sensor (with Code (494) USA version)

Location
The fuel filter with fuel pressure regulator is inserted in the fuel tank from the rear.

Task
The fuel filter filters out the impurities from the fuel and prevents contamination in the fuel injection system.
The fuel pressure regulator limits the fuel injection pressure to about 3.8 bar.





Design
55/2 Fuel filter with fuel pressure regulator
55/2a Fuel pressure regulator
A Fuel feed from fuel pump (M3) (uncontrolled fuel pressure)
B Fuel return from fuel pressure regulator (to fuel feed module)
C Fuel connection to engine (controlled fuel pressure)

Fuel filter, function
The fuel filter element is inserted in a plastic housing and fuel flows from the outside inward. As a result any impurities are trapped.

Fuel pressure regulator, function
The fuel pressure regulator sets the fuel pressure to about 3.8 bar by controlling the fuel return quantity.

If the set fuel pressure is exceeded, the diaphragm is pushed against the push spring and the valve attached to the diaphragm opens the fuel return orifice to the fuel feed module.

If the set fuel pressure falls below the limit, the valve is closed again by means of the push spring.