My '08 FT SD with 23hp Kawasaki that 8 hours on it does not run smoothly when blade is not engaged, the engine acts like it is gasping for fuel. However when I engage the blade it seems to run more smoothly. When the engine is running the bulb on the in-line fuel filter is empty, you can see the gas squirting through but it is not full. Should the bulb be full of fuel at all times? A couple of weeks ago I ran one fuel tank completely out, I switched tanks and was able to restart the engine. Do I need to bleed the fuel line? If so, how?