So if someone could help me figure out whst I'm not understanding I would greatly appreciate it. I will attempt to describe the fuel delivery system in my 68 firebird as I understand it and please correct me as I go astray. Starting at the tank itself I have what I have heard called a fuel sending unit. But since there is no motor, a supply line and a return line, a screen and float. Seems like it can't send anything, just measure fuel capacity. Those two lines go to the mechanical fuel pump where the pump draws fuel by the lever that is activated when you crank the engine. And if all that is correct so far, here is where I get confused. I've heard that the oblong shape of the cam activates the lever, also heard it called a cam lobe, also heard it is activated by the fuel pump eccentric. Then the pump feeds the carb and the magic happens. My problem is the fuel pump is noy pumping fuel. I replaced it and same thing. I did a vacuum test to make sure the diaphragm wasn't blown. On the old pump it wouldn't hold pressure but the new one did, but still no fuel. I ran the supply and return lines to a gas can but pump not pumping when turning the engine over. Tried bench testing it with a can and actuating the lever by hand like I was jerking off. Not sure if that's even a real test. But still no fuel. So.....ya, that's where I am. HELP