Fuel Filter: Description and Operation

GF47.20-P-2101MOR Fuel Filter With Integrated Fuel Pressure Regulator, Component Description
- ENGINES 275.954 in MODEL 230.477 as of Model Year 09 /Modification Year 08 model refinement package
- ENGINES 275.981 in MODEL 230.479 as of Model Year 09 /Modification Year 08 model refinement package





View of underfloor
55/1 Fuel filter with integrated fuel pressure regulator

Location
The fuel filter with integrated fuel pressure regulator is located in the underfloor, on the left of the rear axle differential.

Task
The fuel filter filters out the impurities from the fuel and prevents contamination in the fuel injection system.
The integrated fuel pressure regulator limits the fuel injection pressure to about 3.8 bar for engine 275.954 and about 4.1 bar for engine 275.981 (AMG).





Body
55/1 Fuel filter with integrated fuel pressure regulator
55/3 Valve
55/5 Diaphragm
55/6 Compression spring
55/9 Fuel filter element
55/10 Throttle
55/40 Fuel pressure regulator (diaphragm pressure regulator)
b Aeration and ventilation of fuel pressure regulator
A Fuel feed from fuel pump (M3)
B Fuel return flow to fuel tank
C Fuel (at regulated fuel pressure) to engine

Fuel filter, function
The fuel filter element is integrated in a sheet metal 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 or 4.1 bar by controlling the fuel return quantity to the fuel tank.

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

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