[MikeNH]

my oil fired furnace is buring rich and keeps shutting down i think due to a blocked exhaust. I cant unclog it because i can't see the exhaust pipe inside the chamber. The stack and inside of the furnace where i can access it is clean as is the chiminey.

 

[COLDIRON]

When was the last time the top was taken off and brushed through to the chamber and vacuumed?

 

[beenthere]

Could be other issues, such as a fouled nozzle, or dirty cad cell.

 

[techpappy]

oil burner fan blades may also be clogged..this would result in too little air for combustion...also air intake on oil burner may require adjustment..usually one screw on rotating damper on end of burner..loosen and increase air position a little at a time...OR oil pump pressure may be too low or too high..suggest getting heating tech to check out and set up..too many variables to consider by guessing...smoke test or better still , flue gas analyzer should be used to be sure.