Have you pulled the draw assembly recently?
OK, here are the basics for a Beckett-
electrodes 1/8" gap at center point, 1/8" forward from nozzle face, 1/2" up from nozzle center orifice.
Barometric damper. If you are getting a dirty fire eye, you may be under positive pressure. Breech draft 2wc and stack draft 4wc.
Transformer spark test. turn off oil and start unit, flip transformer up carefully. The 2 springs are capable of 10,000 volts. Take an insulated screw driver and hold post to post to make spark jump. Spark should jump at least 1/2" to an inch. BE CAREFUL.
Oil pump pressure should be 100psi.
air adjusted to bright yellow flame orange/smokey not good. This not a tuneup but should get you close.
Let me know if you have any more questions.
Yes, the barometric damper controls how fas the heat/exhausts gets up and out of the furnace and vent pipe. When the unit is running and the damper is flapping open it slows the draw from the furnace by pulling air through the damper. Like a hole in a straw. This is an efficiency balance. We want to keep the heat from racing up the chimney and not get our moneys worth of heat. But, this if not balanced right, can slow the draft to where the furnace is postive instead of negative. If you opened the inspection door, you should be able to hold smoke in front of it and see it suck into the furnace, when it is positive it blows back. Thus when I see a dirty eye, I wonder why the soot came back to the transformer.
I believe your issue will be electrode settings, air mix, and damper setting. A good oil man can set the draft , pressure, use a correct nozzle and really obtain a pretty efficient burn.
By all means, let me know if you have more questions. If you cant tell I like to ramble a bit about the units.
The electrodes could possibly wear over time but is unlikely. I work on units with 30 yr old points that are fine. The damper should be level and able to swing freely, but without a draft gauge we wont know what to set the counter weight for. If the unit is blowing exhaust out of the inspection door, we want to adjust that damper so it does not open as much so we can force the draft a bit.
The air mix is critical in the process for the unit not to soot up. Sounds like you are getting closer.
That one made me smile....Because I happen to have some experience with flooded oil boilers.....Some stories are better left unsaid.
Throw some lit newspaper in there and have something to prop open the inspection plate. I saw one get so pressurized one time it blew off the barometric damper.
Be careful, and remember, if possible it is best to get it set right with pressure gauges, draft test, smoke test, co test etc.
But this should get you by.