I go to start my Echo edger and the cord is very hard to pull and gas comes spraying out of the muffler when I finally do get the cord to move. I can sometimes get it started by unplugging the fuel line from the carb and pulling the cord until it fires, then plugging the fuel line back in. When I unplug the fuel line, gas squirts from it as if the fuel-tank is under pressure. Once it's running, it typically runs fine until a day or so later when I go to use it again and I'm right back at square one. What do I need to replace to make this stop happening?