Diesel Aux. Heater

[stopping]

Well I have one of these fabulous heater/ funaces on board but it has always smoked inside the van. I want to fix it.

I took it out cleaned it well, checked for leaks from combustion chamber to air space side... No obvious leaking of water from one side side of com chamber to the out side.

All seems to work... it is just the pesky toxic smoke that fills the cab every time I try to use it.

Also it shuts off automatically after 2min er so.

Any help would be great.