Check it for fuel blockages: put a flat roasting pan under the burner. remove dial on fuel valve as it enters the burner. Remove fuel line from burner pump. Reinstal fuel valve dial and check for good fuel flow. If no.. clean and change your filter at the tank. If that is sludged, clean it and retest.. There is also a filter inside the pump. If none of this makes any sense...Call a tech!

You have blinking light on the control panel.count the flashes.you also have diagram inside of furnace cover.#of flashes will point you to the bad or open sensors .good luck

Clean or replace the flame sensor you can attempt cleaning it by pulling it out and using a scotch rite pad on the rod. Just scratch off the black carbon and retry or replace it to be sure