Fuel Filter: Description and Operation

GF47.20-P-2110SM Component Description For Fuel Filter With Fuel Pressure Regulator
- ENGINE 113.987 in MODEL 209
- ENGINE 113.988 in MODEL 203 up to Model Year 8
- ENGINE 113.989 in MODEL 171 up to Model Year 8





Type 171
55/2 Fuel filter with fuel pressure regulator





Model 203, 209
55/2 Fuel filter with fuel pressure regulator

Task
The fuel filter filters contamination out of the fuel and thus prevents fouling of the fuel injection system.
The fuel pressure regulator regulates the fuel system pressure for fuel injection.





Design of model 171
55/2 Fuel filter with fuel pressure regulator
55/2 A Fuel pressure regulator
A Fuel pressure line from fuel pump (uncontrolled fuel pressure)
B Fuel return from the fuel pressure regulator (to the fuel delivery module)
C Fuel pressure connection to engine (controlled fuel pressure)





Design of models 203, 209
1 Fuel pressure line from fuel pump to fuel filter (uncontrolled fuel pressure)
2 Return line from the fuel pressure regulator (to the fuel delivery module)
3 Fuel pressure line to engine (controlled fuel pressure)
55/2 Fuel filter with fuel pressure regulator
55/2a Fuel pressure regulator
B4/1 Fuel gage sensor in left half of tank

Fuel filter function
The fuel filter element is integrated in a plastic housing. The fuel flows through it from the outside to the inside. As a result any impurities are trapped.

Fuel pressure regulator function
The fuel pressure regulator (55/2) regulates the fuel system pressure of about 3.8 bar over the amount of fuel returned.

If the set fuel pressure is exceeded, the diaphragm is pushed against the push spring and the valve attached to the diaphragm opens the passage for the fuel return.
If the set fuel pressure is below the limit, the valve is closed again by means of the push spring.