QUOTE(Danny Vermin @ Oct 29 2008, 01:53 PM)
actually, it was done just before the winter last year, but we also let the tank run down almost to empty, so I'm thinking some sediment from the bottom of the tank might have clogged the nozzles, but I've never poked around with this stuff before.
I'm usually pretty handy with kind of stuff, d o my own car repairs for the most part, or at least I did when I had shitboxes that actually needed repairs more often.
You have filters, probably 2 of them, in the oil line leading from your tank to the burner. Even though there most certainly is residue in the bottom of the tank, it wouldn't have gotten past these filters. Even so, a clogged nozzle wouldn't result in black smoke and a backdraft into your house. Your burner would just not fire.
Oil burners are not complicated, but if you've never worked on them before, now might not be the time. Still, it can't hurt to change the filters, which is easy to do. I don't know how old your burner is, but if it's a newer model, take the top off and see if your heat exchanger is clogged with soot. Take a look in the ductwork for the same problem.