The Beckett AFG is installed in a Tarm 2200 Excel dual fuel boiler. Since installation all oil has come from a new tank, and line. The filter has been replaced recently. Also the entire fuel circuit of the burner has been cleaned and flushed. The nozzle, and controller have been replaced, and the cad cell checked for proper function. What happens is after igniting the flame will suddenly stop. The time sequence has varied after attempts gave been made to correct the problem, for a brief period the flame out did not occur if the view port was left open. Curiously as soon as the view port door was closed the flame out would occur. This behavior was persistent for some hours, until leaving the view port open no longer prevented the flame out. The bucket company and Tarm can offer no explanation or further help it seems. Two competent burner technicians have made efforts to diagnose the cause without success. They are not the "replace and see" type, and have been very thorough and intelligent in trying to find an explanation. We rely on the oil burner to provide reliable back up for the wood boiler and prevent the house from freezing up if we ar not at home so this presents a serious problem for us up here in the frozen north. One thought has been that the specified #6 turbinator be replace with a #3. My best thought at present is that the flame is somehow being extinguished by somewhat violent turbulence with the only possible clue being the transient effect of leaving the view port open which might have impacted the airflow within the firebox. We are approaching the unsatisfactory move of "replacing" the burner having simply run out of alternatives or ideas. The flame does make some considerable noise unlike any prior burner I've had any experience with, but I'm told that is unrelated to the flame out. Any help would be appreciated, and a correct diagnosis will win you great admiration from a number of pros! Thanks, Duncan