Gas and Oil Home Heating Furnaces - Smoking oil boiler

I have a four year old oil fired boiler, (Weil-McClain), that upon firing puffs back white smoke from around the air band adjustment cam setting. I believe that is what the part is called from looking at the furnace manual. This problem developed all of a sudden one day, not over a period of time. . After this puff back, the burner runs for only about 30 seconds then shuts down. The furnace is used mainly as a back-up for my wood-burner, so in the last 4 years it has probably run only the equivalent of 1 year. I installed a new fuel filter, and bled the fuel line. Could the problem be the cad cell eye?, the nozzle?, the ignitor electrodes? I am at a loss as to what to do. In the manual the causes listed for this problem are: 1. Delayed ignition, 2. Nozzle afterdrip due to poor cutoff, 3. Excessive draft, and 4. Incorrect attenuating air band setting. Of these 4 I would suspect #1 or #2, as nothing has changed to effect the draft, and the air band setting has not been altered since the boiler was installed. Any help will be greatly appreciated, as I am at a loss as what to do next. Thanks, DGR

As it said I would look at all of the above. First the nozzle if it set that long the nozzel could have a jell like in it. Put a new one in Then are the electrodes clean and set right. The ceramic on them is clean and dry? Is the air tube clean and dry. Clean off the cad eye. Did you take it apart and move the nozzle in or out any there in the air tube or didnt put it back where it was?Check the transforner and see if it is good and up to full power;) ED

Thanks Ed for your suggestions. I tried what you suggested and got a little improvement. Getting disgusted and trying to figure out what was going on with the burner, I went outside for a breath of fresh air. I happened to look up at the flue pipe, and instead of the normal white smoke, it looked as if I were burning coal. Grey/black smoke was coming from the flue. I shut the system down, and decided that what was happening was incomplete combustion. I removed the access cap on the top of the boiler, and looked down inside. There was a great amount of black soot nearly completely blocking the spaces between the heat exchangers. Not having the proper brush, I poked loose what I could with a straighten out coat hanger and used a shop vac to remove the soot. Got about 1 quart of soot out of the boiler. I then put a trouble light into the combustion chamber and could finally see light up through the top. Put everything back together, fired it up, and it worked. Checked he discharge from the flue outside, and once again only a small amount of white smoke was coming from the pipe. I guess that even though I only fire the boiler up occasionally, in four years time soot can build up. After this heating season I will get the proper brush and do a thorough job, although as of now all is working well. I burn #2 oil, and I guess it is a little dirtier than kerosene. I will now check the boiler before the beginning of each heating season. Thanks again, DGR

If everything is ok with the burner it sounds like you dont have the air set right after it has been burning for a while if you look at it through the peep hole. Just every now and then you should see a little wisp of smoke and thats all. How is the barametic damper doing do you have 2" over the fire draft???
You should be ok with #2 The gun burners should burn #3 but you cant get it anymore;) ED

Sometimes humidity from the air causes the thin coating of sulphur scale in the boiler to swell up and start to clog the passages. When that happens, it's just like reducing the amount of air on the burner adjustment. It restricts airflow. This further causes the smoking/sooting condition which closes the flue passages even more and the cycle continues. That eventually leads to the puff back like you had and will cause a nozzle to go bad from the leftover heat in the combustion chamber after a firing cycle and no residual draft to cool the burner and chamber. You probably have things under control but I suggest getting a brush that will fit in your Weil-Mclain and having the burner adjusted professionally after the boiler is clean. You might consider using a heating oil supplier that uses low sulphur oil. Especially if you don't use the system often. It may cost a few cents more but it would be worth it. Some dealers are switching to the use of low sulphur just like the dieseld burn but it is dyed to eliminate the requirement for paying 55 cents tax on every gallon.

Ken

Sometimes humidity from the air causes the thin coating of sulphur scale in the boiler to swell up and start to clog the passages. When that happens, it's just like reducing the amount of air on the burner adjustment. It restricts airflow. This further causes the smoking/sooting condition which closes the flue passages even more and the cycle continues. That eventually leads to the puff back like you had and will cause a nozzle to go bad from the leftover heat in the combustion chamber after a firing cycle and no residual draft to cool the burner and chamber. You probably have things under control but I suggest getting a brush that will fit in your Weil-Mclain and having the burner adjusted professionally after the boiler is clean. You might consider using a heating oil supplier that uses low sulphur oil. Especially if you don't use the system often. It may cost a few cents more but it would be worth it. Some dealers are switching to the use of low sulphur just like the diesels burn but it is dyed like home heating oil to eliminate the requirement for paying 55 cents tax on every gallon.

Ken