How can i fix my DESA Master B150EB space heater?

Ok i have an old diesel fired Master B150EB which when i plug it in it just smokes and wont fire up, if i hold a piece of card over the back restricting the flow of air it will fire but does not get very hot and then when its removed it just blows out plumes of grey smoke, also if i take the top of the torpedo off and turn it on it fires up ok but again doesnt get very hot, its sparking ok and i can see a nice jet of fuel with top off. I have tried winding the air mixtures in and out while running and together but it wont fire up, ive also taken the internal filter out just to see but this hasnt done any good.

thanks for any suggestions or help Jason.