Rubber on the feeder is worn and does not pull in papoer properly

It may be that paper is non-compatible, too lightweight, curled edge, or damp.
Try raising the in-tray a bit, if you use a bottom-feeder.
I propped an allen-key under my in-tray to lift the angle slightly, which helps 'slide' the paper to pickup roller.
Also 'help' the page by lightly pressing the back edge when it tries to feed.
If your printer's old, the rubber 'gripper' ring on the roller may be worn.

The feeder pin used by hitachi has a shoulder on one side and a rubber washer /retainer on the other. There is only one groove and the retainer fills the groove and if the correct pin and spring, no extra room to fit an exstra retainer unless the shoulder is worn so bad that the pin is falling thru the plunger. I have seen a lot of creative ways that owners use to hold the pin in place due to lost rubber retainer or lost pin. I also see many guns that have installed a retainer pin from porter cable which has two grooves (one on each side of the pin and no shoulder ). Porter cable pin works fine and fits perfect. Good luck

Remove nails from the gun and dry fire the gun by bumping it against thick rubber mat or coiled up rubber hose. As the gun cycles notice the feeder moving back then forward in time with the cycle. Make sure that the feeder is connected to feeder driver with a roll pin and that the check feeder is in place in the latch door. The check feeder is thin metal and should have spring action. The driver should return completely to top of cylinder with some degree of force. There should not be much air leaking out the nose as the gun cycles. If a quantity of air is leaking out nose with each cycle, then lower bumper may have broken/cracked. Replace as needed. If very little air is leaking out nose with each cycle then driver could be bent, piston oring could be worn or lack of lubrication in cylinder. If all lower parts seem good, then only area left to check is head valve. There is a 1/4 inch dia. rubber ring at the very top of head that could restrict air flow out of exhaust port. Adjust as needed. Good luck.

Skipping could be caused by various issues including, worn piston oring, cracked lower bumper, weak or missing feed spring, weak or broken spring behind feed piston, or weak/ missing check spring on door. Easy tests. Open door and remove nails, point gun up then down again to check for loose piston. If piston moves up and down, replace oring and examine lower bumper for missing pieces. Piston should stay at the top of cylinder. Make sure that there is spring tension on feeder and on check feeder on the door. Dry fire the gun rapidly against rubber pad or coiled rubber hose. With door open notice that feeder is moving back and fourth just as rapidly as the driver/piston is moving. If it appears to move slower than piston moves or in slow motion, replace feedpiston spring and oring. If feeder moves just as rapid as driver, remove air hose and push feeder back by hand. It should take a great deal of pressure to move feeder all the way back. If spring feels very strong replace oring to feed piston and make sure that the air pathway to feed piston is clear. Good luck

Please do not use thin, paper substance 20 is good enough to prevent paper jam. happy printing

This is a very popular gun, very light and powerful. Skipping nails is not a common problem. Here are a few things to check that would cause the issue. (First remove air hose and nails.) Worn piston oring (piston will be in the down position). Open side door and check that piston is at top. If oring ok, check feed spring under feeder claw. If spring is in place, push feeder in manually. It should be very difficult to move feeder shaft. If it moves easily then spring inside feeder chamber is broken. If ok, connect air to gun, leaving side door open (nails removed) and bump fire gun against hard rubber (or coiled rubber hose ) very rapidly. While bump firing rapidly, look at feeder moving back and forward. It should be moving very quickly keeping up with speed of driver. If it appears to be moving slowly compared to driver there is an air feed restriction to feeder chamber. Check for debris in small air passage to chamber. Remove two allen screws holding nose of gun to body and examine the small white teflon oring between nose and body(part #149885). Sometimes this oring traps dirt and grime or just simply gets pressed so tightly that center hole is restricted. You must use the correct teflon oring here because the nose and body fit so tightly together that a rubber oring will close air path. Good luck.

Take out the paper and look in the paper feeding slot: you will see a metal rod with seven rubber rollers on it. One of them (the one opposite the crumpling) is not catching the paper properly.

Easy to fix reasons are pieces of paper or debris caught in the plastic "teeth" of the mechanism, which stop the paper from being captured, and the whole rod snapped out of one side's retainers (gently pull it back in position until it clicks. The snapped-out side is the one opposite the crumpling).

The debris might also be just inside the feeder slot, so you'll have to use a strong light and hair-tweezers.

Unlikely-to-be-fixable reasons include worn out or defective rollers, severely snapped-out-of-alignment rollers and a warped rod.

You may get the printer to print (if the rod is intact but mysteriously not catching the paper) by keeping the paper upright with two fingers on the sides, so that one side's rollers only are supplying traction and your fingers supply the steadying. Not very satisfactory, but the "hand-feeding" often works.

You may also get some more weeks out of a worn roller by cleaning it carefully with a cotton swab and rubber cleaning fluid (beware not to use a solvent! "Rubber renewing" sprays are usually OK, just spray some on the swab). Sometimes, dust is enough to get an otherwise good roller out of operation; in this case the trick gets you a couple years' time.

I guess the rubbers that pull the paper are worn out. Replace it.

Rollers may be worn out and not properly grabbing paper or a gear may be broken. You should be able to inspect by lifting cover to feeder and watching as paper is pulled through.

Like a worn running shoes, the paper feed roller of the Automatic Document Feeder (ADF) have lost it's traction and has to be replaced or cleaned. Paper just slids and doesn't picked up properly without that little push. Professional servicers use a cleaner specifically designed for rubber rollers. However, YOU CAN get extra miles on it by dabbing a Q-tip in warm water and cleaning the paper feed roller on the ADF. Like all eletrical devices, the unit has to be turned off and unplugged before working on it. Take all precationary measures and goodluck.