I have an old Echo weed eater and it won't start. i cleaned the whole carburetor, the whole spark system is fine. it's one of those trimmers with the kill switch on top. It has good compression. i took the exhaust off and i can see exhaust coming out so i know its firing. I wonder if it the fuel issue. There's no fuel line or filter in the gas tank. can anyone tell me if i need to put one on to fix the problem?