Srpis300

i have a 2001 lexus is300 i just bought i have been having problems with the fuel pump coming out of the sending unit im not to sure what to do about it i have tried replacing the oring that goes on it and still comes out anything would be helpfully thinking about buying a new fuel pump but not sure yet.. ps the fuel pump that is in it now was a replacement and its like a 20$ ebay fuel pump not sure if its just not enough or what thanks in advance..