pumped gas and it overfilled with only 1/2 tank of fuel.

[bronxnativ]

does your miles driven lead you to believe it only really needs 3 gallons or have you driven 300 miles and know it should need 12 gallons, not 3?
Don't fuss with sending unit if the distance driven and fuel to fill up equals 25MPG or whatever you normally get.
The next time it only takes a few gallons. stop fueling and walk around and turn key on and off and the put more fuel in to see if it fuels normally.
A 96 could have the onboard vapor recovery fuel venting andthe tank vent valve can be triggered to close and stay that way for 12 minutes after key off. Cycling the key resets it. If this is the case then see if the problem is only if you shut it off and cooling fan after-runs.

Will give your suggestion a try. FYI: I drove over 400 miles; car needed gas (was at 1/4 tank), then this happened. For this reason, I know for sure that the car needed gas and 1/2 tank should not have caused the fuel to back out of the filler.