Fuel pump noise

Changed the fuel pump because of a top leak assumed the gasket or overflow was bad. Took out, changed it, no problems in doing so. Was fine for about 2 weeks then one day started making a loud low hum. It's an electrical sound but not like that normal whine you hear when they are going bad, much lower pitch deep sound. Let it sit that night to check the next day and it did nothing. No sound at all. So thought maybe bad gas etc. That was about a week ago. Today leaving work it starts making the sound again but nowhere near as loud, more like the pump priming sound. Noticed when I do anything like roll the window down I can hear the power drain in the sound, you know like the pitch of the sound dropping when I hit any electrical switch. Any ideas? Thanks!