Cleaned and serviced one oil fired furnace with MA. Vacuumed combustion chamber, changed filter, nozzle, and strainer, had to prime oil line with push pull pump oil line is ran very weird and pump doesn’t have enough pull when oil goes back to tank, inspected all water components which look good, performed combustion and efficiency test which everything tested normal did have to make small adjustment CO levels were over 13%, system operational and working.