Primer botton doesn't seem to be doing anything - not pushing gas into carb. Tried elec start allot. Pulled Plug and it sparks just fine. Put a little gas right into spark plug hole and replaced plug. It ran for 5 seconds and died. I don't think it's getting fuel - what can I do before taking it to the shop? Is this vapor lock? Can I pull off the brass-colored thing that the primer tube goes into and do anything with it?