Brushed and vacuumed flue pipe and heat exchanger Replaced oil filter, nozzle, and strainer Checked all electrical connections and safeties Performed combustion and smoke tests While performing the maintenance we found carbon buildup and oil residue inside the blast tube and on the nozzle assembly. Went through the job history and saw the ignition transformer was starting to get weak. Tested the transformer and found the spark was yellow/orange indicating it is weak. A weak transformer can cause delay in ignition making the unit start up rough and cause an oil smell. After getting customer authorization we replaced the ignition transformer. Started and tested the system. Unit is working properly. Noticed 1 section of the exterior of the boiler starting to leak and develop sediment buildup. Recommend reevaluating next year.