Monitor 441 is at least 10 years old. I let the kerosene run out last season and when I went to start it up it wouldn't start. I opened the line from the tanl after the filter to make sure kerosene was flowing and blew into the line to "assist" the flow and tried again. Now the unit starts up and runs for a while with half burner status bars, fan comes on(heat) and burner status bars go to full for about a minute then the unit shuts down with burner status bars blinking. I have run this cycle maybe 10 times thinking air in the line to no avail. Help!