93 325is Fuel Pump

I havent posted in a while, my original problem was no fuel and no start. Found the crank sensor bad, this fixed the problem. after several months the fuel pump quit, changed it out with a after market brand (never heard of) ran good for two week and went out again. Not sure if something is burning up the pumps or just a cheap second pump. After checking power etc to the pump I found dont have power when the key is initially turned to on. When cranking the engine I get 8 volts (battery is a little weak). My questions are
Should I have power with key initially to on?
Could something be burning the pump?
When I get another pump what do you recomend for a good price?