The burner should be tuned up yearly with a new fuel nozzle, blow the J pipe out, remove and clean the electrodes and regap the tips. Carbon builds up on the porcelain insulators, and can conduct electricity away from the tip gap. Fuel filters sould be replaced at this time, too. And every couple of years, the fuel pump screen should be cleaned. The cover on the fuel pump is held on by 4 bolts. Inside that there is a screen. If you keep good clean fuel in the tank and keep the filter changed, this screen may never need to be cleaned.