Function

The plunger type fuel feed pump should pre-filter the fuel and transport it to the in-line fuel injection pump. In addition, the quick air- bleeding of the fuel system should be made possible by a manual pump.

How it works

It is mounted on the side of the in-line injection pump casing. Its piston is moved back- and forth by the camshaft of the fuel injection pump through a roller tappet and a counterspring. The counterspring determines the supply pressure. In the event of an interruption of the fuel supply, the spring remains in the compressed position, thus protecting the pump against damage. Should two one-way valves be installed, the pump transports the greatest amount with every second stroke (simple-action), with four valves it is twice as active, and transports the same amount with each stroke. Larger injection systems also have a manual pump (see above) which is connected to the inside of the fuel pump, this makes it possible to air-bleed the tank faster after repair work, or after allowing the tank to run dry, at the same time also protects the starter and/or the battery. More seldom are pre-cleaners (coarse filter, inspection glass) which enable the pre- filtering of the fuel to protect the fuel feed pump. 09/09

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