I have a Sears Craftsman edger. It was running fine the last time I used it a couple of weeks ago. Now when I crank it, it will run for a second or two and then die. It has a primer bulb on the side of the carb. As long as I pump the primer bulb it will continue to run, but when I stop, the engine dies. I have taken the carb off and cleaned it, but it still does the same thing. Any ideas as to what is causing this?