Someone had recently posted their difficulties in the tractor forum with the filter mating surface on their new Kohler Command. It isn't uncommon at all to find the original filters cranked on- disregarding their own installation instructions. KAW,B&S and Kohler alike. Does your model have an oil cooler that attaches to the base of the filter? Is your's a Courage or Command?

You could have a bad/weak transformer and/or primary controller. This is not a diy type repair as you are fiddling with 10,000V on the transformer. Also, you do not "clean" an oil burner nozzle, you replace it with an identical replacement part. The numbers on the lands of the nozzle indicate firing rate and spray pattern. Your furnace rating plate should specify the correct nozzle. The nozzle gets plugged from the back side. From your description, you are getting oil which is then permeating the house. No ignition is the problem, but be aware that an oil burner MUST be set up with an oxygen analyzer to get the best efficiency. I understand not wanting to hire this job out, but you have about zero chance of getting this to operate well/properlyefficiently without a proper cleaning first and set-up second. Wish I had better news for you, but you will spend the service call money in oil due to poor performance anyway.

The filter should be right at the outlet of the tank in some sort of canister. You can put a second filter right before the burner too.

So the service company came. They did many things to address the rattling door which had no effect: - changed the filter - changed the strainer in the pump - adjusted the air flow next to the pump - blew air through the fuel line back to the oil tank (the burner whined loudly after this then quieted down) - bled oil from the burner - started to remove the flow control from the system then decided it was working fine and put it back Finally they changed the nozzle. They stepped the nozzle down to .75 by 70 degrees and wouldn't you know the furnace is back to its quiet happy self. What a relief! I can sleep again at night. (They did not clean/vacuum the furnace.) The showers have been consistently hot, set at 170, 190, and 15 differential. The tech did not have a tool to test the water temperature. Still need to retest the circulator but much progress!