New Primer bulb for Ryobi 410r Cultivator?

I have replaced the primer bulb and hose, as well as the fuel line and return line; however, my new bulb doesn't want to fill with gasoline so that I can prime the engine. If I pump long enough, I can get barely enough fuel in the carburetor to almost get the engine to start. I have checked and rechecked the connections and they are correct. I got the primer bulb from Home Depot and was wondering if there is such a thing as the wrong size? Any suggestions?