A few thoughts... first, clean the HX. All of it. Get a good brush, and a good vacuum. Make sure the thing is as clean as possible and that you got most of the gunk out. Then go down the check list.
An easy annual item is the nozzle - always replace and chuck, do not attempt to clean, drill, etc.
Electrodes can be adjusted to perfection with precision-ground go / no-go gauges.
The turbulator needs to be clean, devoid of soot, etc.
The external air supply shutter should be clog-free, adjusted per mfgr specs for the particular nozzle/model of burner. Ditto on the internal baffle, if there is one (Viessmann Vitoflames have 2, IIRC).
You should be using a tiger loop. It prevents condensation and water accumulation in oil tank by eliminating oil return line leading to warming and cooling inside heating oil tank.
Are the filter(s) clean? Don't use cheap filters, rather go for a quality filter that has a vacuum gauge built-in that shows whether the oil pump is straining to get oil into the burner - a sure sign of a clogged filter. I used to use Garber. Seemed to work as intended (kept water out of pump).
Ensure there is no water in the oil tank. If there is, find an opportunity to drain it out per federal/ state / local requirements. Water in the tank leads to bacterial growth, tank degradation (if you have an old-fashioned steel tank), etc. Water issues usually rear their heads when people run low on fuel or after fills when the tank is roiling. A floating pickup can help here.
Check the flue pipes and chimney for obstructions, clean as necessary. Double check draft damper for proper operation / installation. Ever find a racoon in a flue? An acquaintance did. Thank goodness the boiler refused to fire.
I'm sure there's more. Only after going through the whole check list listed in the service manual should you attempt to re-light. If you haven't taken the service course, do. It'll save you a lot of headaches.
After successful re-light ensure you have zero smoke (you are using a smoke meter right?) followed by using an electronic combustion analyzer to dial the air shutter(s) and / or oil pressure into perfection.
See OilTechTalk and the Firedragon forums for more specific advice re: tuning oil systems. Last I heard, both owners tour the country giving tuning / service seminars.
If you're not a pro, have a pro with the right equipment (i.e. smoke meter, electronic combustion analyzer, etc.) do it for you. Annually! Even though I am a certified service tech for the boiler I used to service in my home I still hired a pro annually to re-check it, etc.
Ever since I switched our house to gas heat, I have been looking forward to taking that service course too. Not enough time! But even if I were certified to service it, I'd still have a pro look at the thing annually.
Edited by CvW, 22 September 2013 - 02:49 PM.