Help needed with my 68

[Andyboy]

I took some stuff to the goodwill today, but when I tried to start it up it wouldn't start. So I floored It and it started but as soon as I let off It shut off instantly. It took a couple of minutes and started but had to give it gas, and was a little shakey. Got it home turned it off and it started again fine. What do you guys think happen? I thought it might be the fuel pump, but I have to pump the pedal a couple of time so it starts so i know the carb is getting gas. Has anyone experienced this?