Fuel pump or sending unit?

I changed out my fuel pump on my 95 Fleetwood(RWD) and my gauge still reads full. Now I do have a very weak battery that I have to jump off when I get in the car to "exercise" it maybe once a week, so will that(weak battery) be the cause of my guage always reading full causing the cmptr to "reset" before it gives correct readings or is my sending unit shot, and speaking of which, where is it located? I always thought the sending unit/fuel pump coincide with each other as one unit; any and all opinions will be appreciated, thnx...