Can someone help me with this. My '31 Buick has what appears a dual chamber fuel pump, sort of two pumps in one. I'm sure those who have seen one know what I mean. Now some previous owner disconnected the lower part of the pump, leaving the "in" and "out" open, therefore using only the top chamber to pump the fuel. Yet the pump works properly. So what is the purpose of the lower part of the pump as I point with my finger on the attached photo? Thank you for your kind help. Claude Lavoie