My canon pc d 320 brings out a dirty copy how can i fix that problem

SOURCE: canon pc1080f make dirty double image copys

Sounds like a cleaning blade streaking in the drum modual. If this is a used cartrige it might be full of toner and causing the toner to continue to rub against the drum.
Other problems might be the discharge cortron not working. Sometimes if they have a cortron wire they can arc, even in the blocks on the inside and outer board of the channels. If they can be dissasebled with care, they need to be scrubbed, cleaned and reassembled. Most times the entire channel needs to be replaced.
The wires and channels need to be cleaned. Special care needs to be attended to becuase they are hairlike thing wires, they break very easy.
The machine might have a discharge voltage that may not be working to nuturalize the field on the drum. This would retain old images on the drum putting the old image on the copy over and over.
Some machines have high voltages, called "Bias Voltage" which is monitored by a speical circit board, High Voltage Power Board.
These boards are cortron power supplies, sometimes they do fail causing these types of problems.
Also, a worn out fuser roll can retain old toner on the surface of it, and causing the old image to be put back on the next copy after it. The fuser presure roll can retain toner and it can put dirty images on the back of the copies.
For major indepth service repairs, contact this vendor for a service call by a service technition.

SOURCE: how do i clean my canon pc 921

Hi,
these isnt toner problem. The toner when is out, gives light pictures.

These is optics problem or drum unit problem.

You need to clean beneath copy glass, clean mirrors on scaner rail assy, and beaneth zoom lens cover.

If the problem still occurs replace drum unit. Beare in mind that you after replacing of drum unit must do initialisation under service mode.