Are the pins actually labeled? Are they 1 through 5 front to rear? Do you have color coding?
I'll attach a picture of the FSV with the cable connector coming out the bottom. I have another picture (2 actually) showing the wires themselves, but they're a bit fuzzy. This picture is from my '92 CC.
You must be registered for see images attach
You said that #4, I believe, goes to the gauge. So, that single wire feeds the gauge, showing the condition of either tank, depending on the dash switch. True?