Why does my oil furnace smoke after the flame shuts off?
I have a Beckett burner on my oil furnace. It works fine when the flame is burning, but after the burn cycle smoke comes from the fire chamber. I replaced the nozzle with a new one and put a new filter in the fuel line, but that did not help. Can someone help?

The oil pressure cutoff in your oil pump is defective allowing some oil that is still under pressure to drip out of the nozzle. This is what causes the smoke. Post nasal drip is what I call it. A new pump or a oil line solenoid added to the orifice line is in order. It is easier just to replace the pump with like same.