What kind of grease to use on fr350 nail gun for piston o ring

There are several how to videos on that item posted on youtube. Also the overhaul kit comes with instructions and special tools that you may need

The fr350a is completely different from fr350. The fr350a is completely modernized framing gun as compared to the retired version. I do not like repair kits because you are replacing parts that are still good. Instead replace parts as needed. If you state the issue you are having I may be able to recommend the actual part needed. If however you do not have any major air leaks, a lube job will make the gun work great. Use white grease or nail gun oil. Good luck with your repair.

My O'ring kit will fix that problem. I have on EBay. That tool has parts that are becoming obsolete.

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.

Normally I would say you aren't using enough air pressure because somewhere around 80psi (every tool is different) will not be enough to fully retract the driver. At 110 you are fine so that is not the case. I doubt it is broken because a broken driver will still retract unless it broke near the piston. My guess is it needs the o-rings replaced but you can pull the top head and pull the driver out first to make sure. Parts and breakdowns can be found here as DeWalt owns Porter Cable.

PC FR350 diagram

Did you rebuild the tool? If not remove all the nails and unplug air, BUMP nose on piece of wood and does driver fall down? If so the pistion o ring needs to be replaced. Also if this is not the case look for a jammed nail in the magazine/nose area. Next check for a bent driver blade. All the above could cause your problem

Causes of piston not retracting are as follows. Cracked /worn bumper, if cracked air will leak between piston and bumper. Try test, remove nails and dry fire gun against rubber or soft wood; depress trigger push gun against wood/rubber and hold in this position. Piston should stay down and no air should leak past nose. Worn piston oring, piston should not slide down cylinder under its own weight. Loose or missing check seal, remove cylinder and look for black rubber band around series of holes. Band should be in place and fit snuggly. Good luck

It sounds like the air pressure on your compressor is too high..lower it and see if your gun shoots better.

check and make sure your compressor is at the right psi. 120psi. is there any nails stuck in it. there may also be a problem with the seals.

I have seen this problem on several brands of nailers. The solution in most cases was to make sure headvalve orings are sealing correctly. Here is a simple test. Remove the head and place on workbench with gasket surface facing up. Push headvalve all the way in with your thumbs then cover the vent hole with finger and release thumb pressure to headvalve. Vacuum should keep headvalve down untill you release finger at vent-hole. If vacuum does not hold, remove headvalve and examine surfaces for fine scratches and/ or make sure of correct size orings (headvalve should be very snug). Remove scratches with extra fine paper (300-400 grit). If headvalve holds, remove headvalve piston and piston stop. With headvalve spring removed, push piston stop into headvalve and make sure that the piston stop fits snuggly into piston. Also make sure piston stop is not damaged or cracked. A loose fitting piston stop will cause multi-fire. Replace as necessary. Upon re-assembly, lube all rubber parts with plenty of silicone lube (not oil, wipe clean all parts before lubing). Silicone paste/grease is sold at Lowes in the plumbing department (Danco Brand). Good luck and email if you have other questions about this gun.