Important!: How To Load Paper In Paper Tray Properly

Although paper jams occur because of dirty pickup rollers I have found that jams occur frequently because of solenoids in the paper feed mechanism (the assembly that the paper trays fit into). There are two of them and over time the damping foam on the levers get sticky causing the lever to operate late which causes the jam. As a fix I remove the damping foam and put insulation tape on the lever making sure the solenoid works by using a 12v bench psu before reassembling. You will need service manual because Paper Feed mechanism removal is a little complex.

Paper feed problems in Canon Laser Jet Printers are caused by these solenoids mainly in Duplex mode. P3005dn's etc.
Hope this helps solve yr problem.

 Follow these steps to remove a paper jam: 
1. Press the Resume button. 
  If the paper jam does not clear, then go to the next step. 
2. Turn off the printer. 
3. Remove the rear access door. Press the handle to the right, and then pull out the door. 

4. Remove any paper that is inside the printer by pulling it out from the back of the printer. 
  If you are printing labels, verify that a label did not become detached from the label sheet while passing through the printer. 
5. Replace the rear access door securely. 
6. If the paper jam cannot be removed from the back of the printer, raise the printer cover, remove the paper jam from the front of the printer, and then lower the cover. Caution Remove the paper jam carefully as it is possible to damage the 
  printer when removing paper from the front. 
7. Turn on the printer, and then press the Resume button. 
8. Reprint the document. Note If paper jams occur frequently, try using a heavier paper. See the reference guide for paper weight specifications. 

Ok this issue ussually occurs when the roller feed doesn't load the paper due to the following reasons:
1. If your printer is operating for  more than two years or so... gear tear will most likely to occur. If you can open the printer and check everytime the printer initiates after power on ad if the roller feed doesn't rotate but the leftmost rotary gear with the encoder wheel rotates, the gear is most likely to be loose even there is no paper jam nor dust contamination on the rubber and paper feed mechanism. You need to replace the said gear with the encoder strip . A simple solution would be aplying epoxy resin so it will be fixed on the rotary shaft. It may last for quite sometime but better yet replace the gear.
2. The feeder rollers might be dirty and needs to be cleaned and greased the gears.
3. Probable defective print cartridge. Try replacing it with a new one. 

But based on the items above, if your printer is operating more than a year or two, and frequent paper jam is being experienced, gear tear near the motor is the culprit.
  

What specific model of printer do you have?
If it's jamming, make sure paper type is identical. Make sure the quantity is enough for the printer tol hold. Try to reduce the amount and clean the rollers of the paper tray/feeder using alcohol.

Heavy cardstock and certain types of slick or coated paper can cause frequent paper jams. To better isolate the cause of your problem (machine or paper), try a new ream of regular 20 lb copy or laser paper.

• Don't Overload
  Overloading your paper tray can cause paper jams. Your manual may say that your input tray can hold 250 sheets -- but if you keep getting jams, try loading 225 sheets instead.
• Check the Paper
  Check the minimum/maximum paper weights that your printer can handle. Paper that is too thick, or too thin, can cause jams.
• If you still get paper jams after this may be its time to clear the internal of the machine..You might want to have a look at the following link..
• http://lasertoners.blogspot.com/2005/10/laser-printer-jam-fix.html