Upon arrival unit was on but not running. Ran hot water and the water heater turned on with no issue. Checked oil flow and had ok flow. Checked the nozzle and found it was dripping with oil on the end cone and in the blast tube. Replaced the nozzle and started the water heater. We found when the furnace turned on while the water heater was running the water heater would turn off. Upon further investigation we found the oil filter by the wall was starting to get dirty and restricting the oil flow. Since the furnace is closest to the filter the majority of the oil was flowing to the furnace and making the water heater turn off. Replaced the oil filter and bled the oil line. Also removed the oil filter from the filter canister by the water heater because the oil filter at the wall is rated for 2 appliances. Started and tested the water heater by itself and when the furnace was running as well. Unit is working properly.