Fuel gauge doesn't work- A common problem in these trucks are gas gauges that put out erroneous readings. (This problem is common to not just the Dakota, but also the Rams, and many other Dodge vehicles) Some people have had luck with running fuel system cleaner (such as "Chevron Techron"), that might at least help the issue. While doing other fuel tank maintenance, erock92kota discovered that the tabs the unit rode up and down on were messed up, he simply snapped them back in place, and his gauge works again.
Unfortunately, at some point, they integrated the fuel sending unit with the fuel pump, so not all years have a separately serviceable sending unit.