oil-furnace, banging noise

Since a little while, almost every time the burner comes on, a loud banging noise occurs. Otherwise, everything is running as usual. It did the same thing a few years ago, but the repair guys found nothing. The noise disappeared on it's own after wrecking our nerves for a few weeks. This time, it doesn't want to quit. Needless to say, after the last experience, I haven't called the repair service yet. What may cause the noise, how can it be stopped? Any advice is appreciated. Thanks, IS
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"Catstone Farm" wrote in message

You left out some important details.
Is it a "thump bang clunk" or a "grrrr thump thump", if it's the "chugga chugga thump bang", better get out now!
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try--- The Wall -- a group that doesnt piss on questions like alrt hvac does
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I'm no expert by any shake of the imagination, but I used to tune-up my Lennox oil furnace for years....had my own Bacharach kit with which to do it.
It sounds to me as if the oil is coming on and the ignition is a bit delayed...and then when you finally get ignition, there's a lot of oil to be burned...and hence the loud bang. This would be one bang....if the banging continues for a couple of seconds or longer, then you may have poor distribution of fuel into the combustion chamber....could be caused by the incorrect spray angle or flow rate of the nozzle or poor adjustment of the two electrode rodes.
Did you have a reputable oil-furnace service person do a tune-up? Or was it a fly-by-night guy who doesn't use any equipment....I've experienced both...and the fly-by-nighters suck. To tune-up an oil furnace (correct CO2, correct smoke, correct draft, and correct temperature in the stack) one does need the proper equipment.
Just my 2 cents from about 15 years of tuning my own furnace.
Mark

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transformer could be weak--that would cause delayed ignition! Better have a pro look at it!
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