Why isn't my McCullough 16" Chainsaw isn't getting fuel to the carburetor?

I have an older chainsaw. The fuel line and filter are good. This chainsaw doesn't come with a primer bulb (doesn't need/have one). There's a line going from the gas tank to the carb, and another line from the carb to the engine. It runs when gas is put directly into the carb, but will not draw gas from the tank. Any help? (there's gas in it, duh)