Maybe someone can help me with a problem with my raypak 336 heater . Its a year old ran great all last year started it up this month I had flame roll-out and had to replace the rollout thermal coupler. Before starting it back up I pull the burner assembly nothing was dirty at all I also took my camera and took a photo of the heat exchanger to dee if it was blocked by soot i can still see the cooper color on the fins so it wasn't blocked. I put the burner assembly back in and started the heater same thing happened roll out . The burner flame is yellow not blue doesn't look like there's a lot of pressure could the gas valve be bad and not opening all the way?