Fuel pump filter

Fuel Pump

Description - Fuel Pump

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Parts - Fuel Pump

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Issues - Fuel Pump

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DIY Procedures - Fuel Pump

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Filter

Fuel filter is located at frame floor on left anhead of rear axle.

M3 - Fuel pump 55/1 - Fuel filter with integrated fuel pressure regulator approx. 3.8 bars

The task of the fuel filter is to filter impurities out of the fuel, maintaining constant fuel pressure in wide limits irrespective of the fuel pump delivery.

55/1 - Fuel filter with integrated fuel pressure regulator CAN - Pressurization line PUMP - Feed from fuel pump TANK - Return flow to fuel tank MOT - To engine

55/1 - Fuel filter with integrated fuel pressure regulator 55/3 - Valve 55/5 - Diaphragm (membrane) 55/6 - Compression (push) spring 55/9 - Filter element insert 55/40 - Diaphragm pressure regulator A - Feed from fuel pump b - Diaphragm pressure regulator vent line B - Fuel return flow to fuel tank C - Fuel pressure connection to engine

The fuel filter consists of a sheet metal casing with an integrated filter element (55/9). The fuel flows through this from the outside to the inside. As a result any impurities are trapped.

The diaphragm pressure regulator (55/40) controls the fuel pressure of approx. 3.8 bar (operating pessure) via the fuel return flow quantity to the fuel tank.

If the set fuel pressure is exceeded, the diaphragm (55/5) is pushed against the push spring (55/6) and the valve (55/3) attached to the diaphragm opens the passage for the fuel return to the fuel tank (B). If the set pressure is below the limit, the valve is closed again by means of the push spring.

Fuel pressure as a function of the fuel pump delivery

A - Fuel pressure in bar B - Fuel pump delivery in liters per hour

A greatly varying fuel pump delivery (e.g. 20 or 140 l/h) does not have any great effect on the fuel pressure.