I have a pretty good understanding of mechanical fuel pumps in a carbureted car but one question.When the carburetor fuel bowl is full and the carburetor fuel inlet
needle valve is closed, how does this cause the fuel pump diaphragm spring not to release and force more fuel through the outlet valve? Is it just the presence of the fuel in the line to the carburetor, that fuel being unable to go anywhere that prevents the diaphragm spring from releasing?