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

Brian, when you did the timing chain, you had to replace the fuel pump eccentric exactly as it was before. It consists of two round cups. The retaining bolt is off center so the cups look out of round. There is a locating tab on the inner one. It goes into a hole on the timing gear. So as the camshaft turns the gear, the eccentric rotates out-of-round and pushes the arm on the fuel pump. The way to test is to remove the fuel pump, push a wooden rod into the fuel pump hole, and hold the wooden rod against the eccentric, and have someone crank the engine. You will feel the rod get pushed in and out. It is easy to get it wrong and unfortunately the only fix is to remove the timing cover and re-situate the eccentric.

Another thing is, you are right, no pump in the fuel tank, just a gauge and filter. The gas line is angled down towards the fuel pump. If you disconnect the rubber hose that jumps from the sub-frame to the pump, gas will drain out of the tank. This way with the car level on the ground, gravity will feed gas to the pump. The pump feeds gas to the carburetor. I'm not sure what year this started, but on most AC equipped cars, there is a third fuel line that recirculates the extra gas back to the gas tank. This is to keep fresh cool fuel at the carb and help prevent vapor lock. Otherwise there is just a supply line and a carb line.

Thanks buddy. I do remember lining up the eccentric. I'll double check it like you mentioned. Do they go bad? Or just improperly installed? Cause I've had it running before so unless they go bad, I would have had to have it installed correctly. Biut ready to say f it and go with an electric fuel pump

No, they can outlast the engine. One cup is retained by the bolt, the other spins around it. It is lubricated by oil spray from the camshaft gear. So the part that the fuel pump arm rides against is actually spinning- very little friction. You may have missed the locating tab, or thought it was tight enough, or accidentally clamped both cups solid. Don't feel bad if you messed up, we all do it at least once. But if it checks out, look at the fuel pump. I have had brand new ones be bad out of the box. These days they can sit on a shelf a LONG time.

No fuel pump lasts forever, especially one that has been used and sitting on an engine that has has gasoline run thru it, the diaphragm rots away like every other piece of rubber on these cars