Fuel tank/gauge problem

[atcq110]

I have a 93 hatch with a red top sr. My car runs out of gas with a 1/4 tank left on the gauge. If you fill it when it is nearly empty it will only take 11 to 12 gallons at the most. I know that something is wrong because the tank should hold 16 right? My thought is that there is something wrong with the fuel pump. This is something I need to upgrade anyway but I was just wondering if anyone had a simillar problem. Thanks