Can the cylinder inside the nail gun wear to where the piston will not hold its self up after fireing

If gun firing but nails not being driven could be one of two basic problems:
1. Nail jammed in magazine not allowing nails to move up.
Empty magazine, does follower move to top of magazine. Push gun against work piece, does fan motor start? Yes - jam in magazine or lock out bar not operating. (this would allow nail un to fire when out of nails)
2. Piston/driver not returning fully after firing, hence driver blade on top of next nail instead of behind it. This could again be caused by a jammed nail or just a nail head. Another case of not returning is the combustion chamber not making a good seal, check O rings on framer (they are steel rings on bradders) it may just need a good clean it is surprising how dirty they can get and if not cleaned a build up of dirt could break a seal. If not been cleaned for a long time worth checking piston rings, worst case scenario dirt builds up around the rings and stick fully in requiring new piston if the rings will not come out.
Nail guns work on the principle that an explosion pushes the piston driver forcing a nail into the work piece, after the explosion a vacuum is created and it is this that 'sucks' the piston/driver back up the cylinder.

As a safety precaution, nailers have incorporated a safety foot that will prevent the gun from firing unless you push down hard. Some guns also have a system where the gun will not fire at all if there are no nails in the gun. To dry fire this type of gun you must pull back the pusher or open the side door. If nails do not feed properly, check for wrong nails, bent rails or weak pusher spring. If all is good with rails and pusher, suspect that the driver/piston is not at top of cylinder and lower part of driver blade is preventing nails from advancing. Remove airline and push the driver to top and retest. If driver is slipping down the cylinder under its own weight, replace oring. Good luck

If a gun is firing and nails are not being driven into the work it's because of one of two problems. The nails aren't feeding fully under the driver or the driver isn't fully retracting each time the gun is activated. Is looks like you've eliminated a feed problem so you are going to have to take the gun apart to find out why air is not being held in the bottom of the head long enough to push the driver back up the cylinder. Go to www.ereplacementparts.com and bring up your model so you can follow along. Remove the four screws holding the head cap on. The things that can cause your problem are: the piston seal & o-rnig are damaged, the cylinder is badly scored, the o-ring & cylinder ring on the bottom half ot the cylinder are damaged or out of place, or the driver guide under the bumper is broke or missing. If it turns out internal parts are damaged or missing, I highly recommend the overhaul kit to replace all the 'soft' parts inside the gun as long as you have it apart.

If the nail will not advance, easy test will determine problem. Open door and remove the nails. Lightly tap the nose of the gun against coiled rubber hose or soft wood with door open. If the driver falls to bottom, the piston oring needs to be replaced. The driver should stay at top of cylinder. Next pull back the feeder to rear position and check for tension. The feeder should spring back towards you when you push. Finally, the check paws on the door should return to extended positon when you push on them. Replace springs as needed. Connect air to gun and rapidly bump fire the gun against rubber. The feeder should move back and forward just as quickly as the driver moves. Good luck

May be due to broken tip. Easy to check. Remove nails and leave door open. With door open, lightly tap the nose of the gun against coiled rubber hose or soft wood. The driver should stay at top position. If driver falls to bottom of the cylinder, replace piston oring. Now press nose of the gun against old coiled up air hose or soft wood and squeeze and hold trigger. The gun will fire and the driver should stay in the down position untill you release the trigger (if not single fire trigger, if single fire trigger remove trigger and press the trigger pin with finger). While the driver is down, make sure that the tip extends past the nose about 1/4 inch (if air leaks past the nose in this position, replace lower bumper). If the driver does not extend past the nose, replace driver. Good luck

Here are a few tests for you to try. You will need a piece of rubber or coiled up old hose.
First open side door and remove nails. Tilt gun head down then up again to check if piston is loose in the cylinder. The piston should stay in top position. If piston drops to bottom of cylinder remove head and replace piston oring or apply some layers of teflon tape under oring to expand oring slightly untill piston stays at top but still can be pushed down cylinder (look at the lower bumper to make sure that it is not cracked or missing pieces, if it is breaking up the pieces can lodge within the air path to the feeded piston). If driver piston now stays at top, connect air to gun and with side door open contact gun to rubber firing gun noticing the feeder movement. With very rapid firing of the gun, the feeder should move back and fourth just as fast as the driver moves. If the feeder seems to move slower than the driver moves then check/replace spring in feeder piston chamber. If spring seems strong enough in your opinion then problem is restriction in the air supply to feeder, if air path is clear then replace orings to feed piston. You will need to remove the two 6m allen screws at front of gun and split gun apart to check restriction at the oring sealing these two parts. Sometimes debris traped at oring (white oring) will restrict air to feeder. Good luck.

When you trip the safety and fire the gun, the cylinder drops down into body of gun allowing a rush of air to push piston down with force. If the cylinder fits too tightly in body, it will not open enough to allow full air pressure into cylinder. Remove head and check that the cylinder moves rather easily down then back up (it should travel about 1/4 inch). If is difficult to move the cylinder then remove it and replace all the orings that contact its surface. Also make sure that the outer part of the cylinder is smooth where orings contact. If there are fine scratches, remove them with 400 grit sandpaper. Lube cylinder/orings with silicone paste lube. While cylinder is removed check that lower bumper is in good shape with no missing pieces. For best performance, also replace the three orings on the feed piston. Piston /driver should move down cylinder with only slight pressure yet it should not drop down the cylinder under its own weight. Good luck

This is an easy fix luckily usually it means that the chamber is dirty and all you have to do is open the top front of the gun so that you can see the piston then take a q-tip and clean the area really well sometimes it requires a degreaser and then when you think that you have it clean make sure to lubricate the chamber really well with the paslode lubricant that came with the gun or they sell it right next to where you get the nails. Then the gun should work fine with no problem if this does not work then this means that the piston might be bent and that could turn into a big problem but is still fixable just harder.

Hope that this works for you

If the piston/driver is broken, the gun will fire however nailing will not take place because the piston will jam in the cylinder. Sometimes the cylinder will also crack when the driver goes. If the piston is not broken but stays down, then check the cylinder check valve, worn lower bumper, bent driver or cracked cylinder. 18 guage nailer has a very thin driver which will easily bend or break. Parts however are not expensive.

joe it sounds like you have damaged the return puck inside the cylinder. when the piston bottoms out their is a rubber puck inside that cause recoil.over time it can become hard and no llonger resiliant - when you dry fire it can shatter or crack . if it does not have this then it just needs oil . are you oiling every use? usually 3 drops at start of daywill run them for years. at any rate you will have to do the following to confirm. diconnect air - remove four crews that hold cover or back of cylinder- should be obvious-lift off cover - this will expose back of piston whick is connected to drive pin. you mat have to push it backwards through guide late to eject completely.Inspect cylinder and piston -is it dry? no oil? inspect o rings around piston there will be two one at top and one at bottom. oil with damp oil cloth and reassemble it reverse. take care to twist cylinder to line up drive pin- this is critical.Do this and get back to me. good luck