What type of device are you using to light your pellets? If you are using anything less than a propane torch like the one I suggested in the above link, I would upgrade.
If you are using a good propane torch and are still having problems, my guess is that the problem is either not enough air flow or your pellets may be too moist.
Air flow can be resolved by a number of different methods. If you have a Jerky Dryer (which you should if you are smoking sausage) you can add that on top of your smoker. I haven't tried this yet, but I have been thinking about adding couple of pencils or some other means of raising the jerky dryer up so it is not directly on top of the smoker, because I don't really want to have all of the power or the jerky dryer pulling that much air through the smoker. The reason that I say this, is because in the past when I have tried this with the dryer right on top of the smoker, my pellets seemed to actually catch fire and burn way tooooo fast. So, my thought is to reduce the effectiveness of the jerky dryer by raising it up a little higher than the smoke hole. Like I said, I have not tried this yet. But, the logic seems sound to me.