Just curious,,,, real curious. How long does the Ryobi battery last between charges, and does it by chance come with two batteries? The reason i am asking is that it takes me right at 1 1/2 hours to 2 hours to weed eat everything on average. I would love to go to a cordless electric if i knew it...
You said your primer bulb is stuck in like it has vacuum on it right? If that is true then the problem with the bulb is between the bulb and the fuel tank. The primer bulb supply hose is all it could be. The bulb sucks the fuel from the tank by creating a vacuum when you let the bulb come back...
Your fuel tank has 3 small hoses in it. One supplies fuel to the carburetor and one supplies fuel to the primer bulb. The other is a return line from the carb so when yor prime it you won't flood it. Most likely the one from the fuel tank to the primer bulb has collapsed. Good ol ethanol gas...