We have a Yukon Plus 85-1500M with a Beckett Model AFG. We ran out of fuel oil and refilled. The furnace has been running great after the re-fill for about 3 weeks. Then all of a sudden the motor starts runs for about 10 seconds and turns off. We replaced the filter at the oil tank and the air breather filters. We bled the line till no air bubbles where showing and it's still doing the same thing. Any help would be great. Thank you

First is the unit pumping oil into the combustion chamber when the pump is running?

Second is the ignition transformer providing high voltage for the spark electrodes to lite off the oil spray?

Is the electric eye (cad cell) clean and looking at the flame area?

These are the first two items to check.

If your burner has not been professionally tuned in the past year now is the time to make that phone call. It will cost you for the service BUT you will save money on fuel oil expense since a good clean running unit will consume less fuel.