Generally there are several aspects, one is the non paper, or paper rubbing wheel not rub into the paper, or paperboard, easy to find. Two is not installed in place when toner, heavy, not to see what is right and cartridges connected, it is spring, clean installed in place. The front cover three is not installed in place, or detector dirty, blowing. Four is the linkage lever dirty front cover, too much resistance, leading to cover can not be put in place, the cleaning and oiling. Failure phenomenonBj2service manual download site