The 2 big wires are + and- for the pump, the 2 small ones are for the sender. Take the plug off (retainer slides back) and it might be obvious if you have a burnt connector.

Fuel pump is RH(passenger side)

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)