Fuel guage question

[SamHatco]

I just fired up my car this weekend and I've run into a snag regarding the fuel gage. I'm installing an 04 GTO interior in my 69 firebird. The wires leading to the sending unit are as follows:
1. sending unit signal
2. low reference signal
3. 5 volt reference

When I took the sending unit out of the tank, I was able to get the guage to operate by attaching the sending unit to the sending unit signal wire, and the low ref sig and 5v ref wires to the body of the sending unit. When I move the arm from empty to full I got the guage to work. When I installed the sending unit back into the tank the guage would not work. I believe the problem lies with the fact the sending unit is now grounded when in the tank.

Any ideas for a work around or dialogue is greatly apprecitaed.

Sam

[SamHatco]

OK, been working all day on this puzzel. I've found that when the sender is grounded then the gauge dosen't work at all, so that leads me to believe that I have to get the low reference signal wire attached to the sender with out it grounding out. I've discovered a new problem however.

With the sender out of the car I attached my multimeter to the sender to check ohm values and I get 240 ohms at empty and 40 at full. The gauge needle will move to full and empty correctly. When I connect the low reference wire to the sending unit and check ohm values the meter jumps to 597 ohms at empty and of the charts at full. WTF? Is there some diode or resister that can attach to the low reference wire to counter act this phenomenum?

When I operate the sending unit the gauge shows full, at 1/2 empty the gauge show 3/4 full and the only way to show empty is to have the float at full empty.

Any ideas out there? I'm stumped

Sam