Performed an heating maintenance. Changed the nozzle filter and strainer. The old nozzle was clogged. The boiler was extremely dirty. Cleaned the heat exchanger and flue pipe. Tested the transformer. It is starting to get on the weaker sign. May need to replace in the future. Adjusted the electrodes. Started and tested. Adjusted the oxygen levels to 8.0%. Had 7ppm. No smoke. The gasket for the top clean out cover is gone. I put furnace cement all around where the gasket would have been. Could have been part of the issue as to why it was so dirty.