1. Could you have gotten the lines crossed on the bulb? Do you feel a suction that would suck fuel?
2. Did you check the ports on the bulb for restriction? One side should pull and the other pushes fuel.
3. Did you check your tank�s fuel filter for restriction by removing it off the line?

I just experienced the same problem and the bulb actually showed signs of a vacuum. Plus, it would not fill until I cleaned the filthy screen inside the carb. This is very easy with compressed carb cleaner or "Low" compressed air if there is no varnish (with air pressure pushing the screen "in" vs out or it might come out). If help is needed, I have seen good "YouTubs Etc carb rebuilding" and good text instructions online.