Hand fed furnace advice

hi, I have a viking junior 4100 hand fired coal furnace. i'm having an odd issue. The cleanout in the back is smoking. it's a little hatch thingy at the very bottom of the furnace in the back. it's quite a was below the fire box about paralell with the as door. now the odd thing is that the ash door doesnt smoke and neither does that main door. when i have the door open that hatch leaks. the smoke would have to travel down to get to it. if it was a proper draft problem wouldnt it be coming out the front too?

also, my coal this year sucks. very duffy. mosty dust. it has a tendancy to melt into a big block and just simmer. i'm not getting 1/4 of the heat out of it that i usually do.

any and all advice is welcome!

Are you burning bituminous coal? Have you checked/cleaned the chimney, maybe it's clogged with soot?

i honestly don't know. i'm in cape breton nova scotia canada. and we only have two varieties o coal available. lump, and stoker coal.

edit: i just found out it's bitimus, thats what we have here locally.

i'm unsure about the chimney, as when i make a wood fire in the urnace it burns quite nicely.

Is this cleanout for cleaning ash/soot from smoke passages? Can you see soot buildup in it?
It sounds like the coal you are using is poor quality and probably causing heavy soot buildup in the furnace and chimney so I would check and clean them if necessary.

The melted together coal and the smoking hatch may be related.

I've had the coal melt together and bridge over the fire to the point that the fire can't breath and the fire goes out with plenty of coal to burn.

Try taking a poker and breaking up the bridged coal, opening up the airflow and heat from below, maybe this will take the pressure out of the area below the fire.

Greg L