6310 has a fine black line down the entire length of the page

Check your flat bed and Document feeder scanning glass need to be clean, if any dot or dust in scanning glass of document feeder it will appear a line, check this points first
1- Check printouts from computer or FAX if it is clean problem in scanning section
2- Check using Copying a blank paper using only Flatbed if it prints without any line its problem from document feeder Scanning glass
So solution is clean the Document feeder scanning glass using wet cloth, note careful about wet cloth switch off the machine and clean it

CClean The MX882 ADF (Automatic Document Feeder)

Be sure to turn off the power and unplug the power cord before cleaning the machine.

• The power cannot be turned off while the machine is sending or receiving a fax, or when the received fax or unsent fax are stored in the machine's memory. Make sure if the machine completed sending or receiving all the faxes before disconnecting the power cord.
  

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• The machine cannot send or receive faxes when the power is turned off.
  

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• If you unplug the power cord, all the faxes stored in the machine's memory will be deleted.
  

  
  

  Print the necessary faxes or save them to the memory card/USB flash drive before unplugging the power cord.
  

1. Open the Document Tray.
   

   
   

2. 
   

   
   

3. Open the Document Feeder Cover.
   

   
   

4. 
   

   
   

5. With a soft, clean, lint-free and dry cloth, wipe off any paper dust from the inside of the Document Feeder Cover (A).
   

   
   

6. 
   

   
   

7. After wiping, close the Document Feeder Cover by pushing it until it clicks into place.
   

8. 
   

   
   

9. Close the Document Tray. speed printer service
   

   
   

   http://www.smoothprinterservice.com/
   

Open the Top Feeder Cover
Clean the Roller with lint free cloth.
Lift the Roller a bit up and you will find a glass strip underneath the rollers
Clean the glass strip with cloth and close the feeder
Try scanning or copying. it should work

Regards,
Ron

Open up the document feeder and clean the scanner glass

You load the originals print side uo on the document feeder tray or print side down on the glass.
To send a single page fax you can either load the original on document feeder tray or on the glass; to send a multi-page fax you must use the document feeder tray.

The position of the paper is the same either you copy, fax or scan.
All this is clearly explained in the user's manual, that you should read and you can download from HP support pages for you printer:

try cleaning the rollers with water in the feeder at the top check the glass too too see if it's dirty

All you need to do is clean the top feeder which opens into two parts. make sure you clean the black rollers as well as the small strip of glass you will find when you open the second part of the top feeder . don't be afraid to pull open the top feeder it won't break

Open the document feeder and clean the scanner glass

Open up the document feeder and clean the small scanner glass.

You sure can - the issue is that there is something on the thin strip of glass where the copy goes through from the feeder at the top - follow these directions and you should clear the problem right up.

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00671260&cc=us&lc=en&dlc=en&product=1119598&dlc=en&lang=en