Fuel transfer system - Vehicles with 8 - cylinder engine: Function

Vehicles with 8-cylinder-Turbo engine possess 2 fuel pumps: The Fuel pump -G6-, which sucks in large quantities fuel. It supplies the Transfer Fuel Pump -G23-, which is responsible for the fuel pressure.

The voltage supply of the two fuel pumps is made by the Fuel Pump (FP) Control Module -J538-, which switches the heading for tension for both pumps depending upon engine requirement between 10 V and maximally the available of on-board tension. The Fuel Pump (FP) Control Module -J538- is supplied via the Fuel Pump (FP) Relay -J17- with on-board tension and connects these through directly to the pumps or reduced if necessary this tension to 10 V.

In accordance with the following condition the pumps are headed for:

• When engine starts, the fuel pumps -G6- and -G23- are supplied briefly with full on-board tension, in order to guarantee snap pressure build-up.
• When driving, the fuel pumps -G6 and -G23 being supplied 10 V are operating. With exceeding of an engine fuel consumption of 90 l/h for both pumps, on-board tension are raised. When falling below a fuel consumption of 64,8 l/h the pumps are addressed with 2 seconds of delay and supplied again with 10 V.
• With engine running, the voltage supply of both pumps takes place for 5 seconds with on-board tension, in order to avoid bubble formation caused by vapor.