fuel gauge 1994 940

[sickboy]

1994 940 BF230 2.4L 4cyl 140K miles 4dr LH steering sedan.
Fuel gauge was intermittent, now it hasn't worked in a month or two. The sending unit is in with the fuel pump. (Combined Tank Unit) I can see only a black and pinl wire coming from the tank seal. In the trunk though, the black and pink wire have joined up in the same harness with a brown and a grey/white wire. The electrical schematic shows that the brown and grey/white wires go from the sending unit to the fuel gauge. Do they all come out of the same connector on the combined tank unit? How do you test the fuel gauge wires? I have read (I think in the Volvo Vadis Program) that there was a bad ground in some models and it showed attaching a new ground wire from the back wire to the body of the trunk. Any ideas?