I have the same problem on my 03 V210. It uses the Rochester Sending unit (240-30 ohm). Based on the chart on page 2(
http://www.rochestergauges.com/Pages/PDFs/DS_953.pdf), mine has a grounded wire between the gauge and sender. Only problem is the wires run from the sender into the wiring harness in the engine compartment and join all the other wires before heading for the gauge. I still haven't been able to trace the wire. I did measure resistance at the sender and it seemed to vary in the appropriate range (depending on how much gas I thought was in the tank). If you can find out what the resistance range is for your sender, check it with a partial tank. If it reads the OHM reading for a full tank, you'll know it's the sender. If it reads somewhere in the middle, it's probably a short or bad ground. There, now you can be as frustrated as I am. Hope this helps.