the fuel switch has essentially two positions, in or out corresponding to left or right pumps.
it has 6 pins.
pushed in its connects 5>6 and 8>9
release or out it connects 1>2 and 7>8

yet the plug from the car body has 6 wires connected to it.

i just think i am missing something. i assume it a circuit for each of the 2 pumps in the boot which draw their earth from car body earths in the boot not from a cable earth.

so what is the last set of wires for? or the final circuit?

 

Switching of the fuel gauge probably. Not sure if the S2 is greatly different but in my car there is just one pump operating with ignition on. The fuel switch controls solenoids that control which tank fuel is drawn from, and which tank the gauge is measuring (unenergised/switch in>left tank, energised/switch out right tank). Fuel return direction to the correct tank for EFI cars is also done via solenoid but that is daisy chained in the boot. EFI cars also have lead the goes of to the EFI system.

Others may chime in if the S2 is different and I am speaking with forked tongue.