Oil-fired boiler, every once-in-awhile it spits out huge amounts of
soot, 1st time thought it was a home-grown outside combustion air pipe
that had slipped 1/2 off and blocked the intakes, because when I took
that off, it ran fine.

A month after that (monday), it did it again, called the service guys.
They said the electrodes were too far apart, was causing late ignition,
and that it wouldn't burn properly bacause of that.

Today, same thing. Wouldn't even start, it was running so 'rich'.
Noticed the air intake was all the way shut, leaving just the small
'default' openings on the pump face open. I talked to the service guy,
priced out a weekend service call. Ummm, no way, given that they
supposedly 'fixed it' on monday.

I asked how hazardous it would be to try opening the air inlet- he said
it might get me through the weekend, since the prob might be a bad
nozzle that wasn't atomizing sufficiently.

Opening the air intake a bit fixed the hard ignition/smoke, but if I
opened the air intake up beyond a small amount, it would blow exhaust
out the damper door, and this is a unit with a power vent.

So air intake closed (as the service guy left it), blows smoke/soot and
stops running, open a little it doesn't smoke and the damper draws air
from the room (garage), opened too much and it blows exhaust out of the
damper door and into the room.

Yes, I know, whatever tuning this thing needs is shot to hell, but its
running without soot and the power-vent is drawing plenty of air out of
the room via the damper, so I'm going to run it until monday.

What the heck does it sound like the problem is? I'd really like to
have a list of possible issues to discuss with the service guy, as I
really want to get this fixed once and for all.

What I see is that the air intake was completely closed, and the other
air intake openings are very small, so that just seems a little odd.
maybe with a clean nozzle that's OK? Maybe someone put a very small
nozzle in this thing, and the air intake really can't be properly
adjusted for that small a nozzle?

Any thoughts out there?

Dave