I'm trying to make a blonde ale here and the darn thing won't stay lit when I lower the flame. Sounds like it's getting plenty of gas but to get a manageable boil it just sputters then goes out and the tank is 3/4 full so I know I have fuel any time I increase the flame the boil gets way to vigorous and I mean like jump out of the pot vigorous. The burner is a couple years old and the burner itself is a little rusted. Could it just need cleaned?