Question

Hi,
I have a 1993 Volvo 940, my fuel pump quit working. It had one pump in the tank and I took it out. The "experts" at Autozone sold me a smaller pump that I adapted to mount to the fuel sensing unit. They convinced me the pump was a repalcement pump and the pump instructions said the pump may not look like the original pump. But I believe the pump I bought and put in needs to go with an additional external pump near the fuel filter. The car will barely start and will not run I guess because it is not getting sufficient gas pressure. After messing with the pump I took out, I 'tightened ' the top of it down tighter (which is a electrical connection cap of some sort) and it will run now when put on 12 volts. My first question is, can I buy a new external pump and add it to my system near the filter since I already put a low pressure pump in the tank and if so, how would I wire the pump? Second question, maybe now that the other pump is running, maybe I should just put it back in