Fuel Pump Issue

I have an issue with a gas station installed fuel pump that is actually on my 96 Grand Cherokee but I imagine it couldn't be that different than my regular Cherokee. They have installed a total of 3 pumps and it continues to do the same thing. The pump itself works fine. The gas guage however, when I top it off goes to "Empty." It may stay there for only a couple of seconds of driving or it may stay there for several days. I've repeatedly checked the wiring and can only surmise that maybe something is wrong with the float. This never happened before the pump was installed. Are the float and the pump seperate entities? Is it possible that they screwed up the float while installing the pump? I have no clue. Any info would be appreciated.