My Ryobi C430 won"t prime (no gas will go into bulb when I squeeze it) It was fine 2 weeks ago.

Any suggestions to how to fix problem?

 

Could be a bad bulb, or the fuel line leading to it has cracked or leaking. Double check it at the fitting on the carb.

Is this a bulb fitted on the carb or is it on a separate mount?

 

Can also be a clogged filter inside the fuel tank.
Been using non ethanol fuel?
If not it can destroy the carb, fuel lines, bulb.

 

All bulb type primer 2-cycle carbs have at least one check valve that closes preventing air from entering the bulb (on the carb side) when the bulb is expanding and should be pulling gas from the tank. If you can provide the make and model numbers of the carb, I can hopefully provide you with more specific info.