Hey guys I have a echo cs5500. Should the fuel tank pressurize and push fuel out of line when I tighten the gas cap. Saw will idle 20 second and go dead and when I pull fuel line off no fuel. I can tighten the crap out of cap and fuel comes out few seconds. Other saws I work on fuel won't stop coming out until I Crack open gas cap. Vent seems ok gas cap is sealing and gas line grommets are new and tight. What's really getting me is if I pepper throttle and get it to Rev up it will keep going until I let off then dies immediately. I pull line off no fuelor no pressure. Am I on the right track guys any help is appreciated?