Porsche 2012 911 GT3 CUP Technical Manual page 44

4.2.2. Reserve pumps
4.2.3. Main and in-tank pumps
A reserve fuel pump is fitted as standard and is activated from a switch
mounted on the dashboard. A warning lamp in the push button is
illuminated when the reserve pump is running.
A switch mounted on the dashboard can be used to switch between the
various main and in-tank pump modes:
 Service: Normal operation
Middle position: Fuel pumps off

 In-tank service: Only the in-tank pumps are in operation
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