Intallation examples of electric fuel pumps illustrated in block diagrams

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Information on diagnostics

What is the difference between in-line pumps and in-tank pumps? When are pre-feeder pumps needed? What are the different installation options for electric fuel pumps? This article tells you all you need to know.

We distinguish between in-tank and in-line pumps, depending on how the fuel pump is installed in the vehicle.
  • In-line pumps are inserted in the fuel line.
  • In-tank pumps are installed in the fuel tank. In the case of in-tank pumps, other components, such as fluid-level sensors or diagnostic systems, can be installed directly in or on the pump module.

Mixed and special systems, such as semiin- tank pumps (e. g. in the Golf II), are not described here.

One or two fuel pumps are connected in series, depending on requirements.
  • A single fuel pump
  • Two fuel pumps (pre-feeder pump, main pump) Pre-feeder pumps deliver the fuel to the main pump under low pressure
  • A single two-stage fuel pump

These installation options are illustrated in the adjacent diagrams

In-line fuel pump


In-tank fuel pump


in- line pre-feeder pump with in-line  main pump


In-tank- pre-feeder pump with in-line main pump


in-line two-stage fuel pump


in-tank two-stage fuel pump, fuel pump in reservoir ("swirl pot"); stages sealed against one another

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