Porter Cable FN250A Driver not retracting

[rwbil]

I have a Porter Cable FN250A Finish Nailer. It shoots fine, but the piston does not retract to allow the next nail to enter, so I have to retract it manually. I opened up the gun and everything appeared to me to be in good shape. I can manually move the piston up and down. It seems to create a seal with a vacuum suction sound when I move it up and down. Everything seemed to be oiled well inside. The plastic cylinder ring was in good shape. I am thinking about ordering the driver rebuild kit, but thought if I understood the theory of operation better, maybe I could figure out the problem. I am guessing here so if someone could explain the theory I would appreciate it. I noticed in the cylinder there are small holes. I am assuming the air enter through those holes normally pushing the piston assembly up. And then when you press the trigger the air is redirected to the top pushing the piston assembly down. I noticed when I push the piston assembly down it goes below those holes. Also could some air be direct up and pushing the piston down? Lastly what does the bumber do and how does it play a role in the piston retracting. Repairing would be easier if I had seen something obviously broken. Any help would be appreciated.

Thanks in advance,
Robert

[rotti1968]

I suggest you do a complete cleaning and rebuild of the unit. I dont mess with just doing a driver rebuild , the complete overhaul takes care of everything and its very easy to do.
unit need porter cable part #903789 complete overhaul kit

heres a little info on how they work
http://www.ehow.com/how-does_4965124...-gun-work.html

[rwbil]

Let me add to my question. When I took the gun apart I could pull the cylinder up about 2" or so to the point the small holes were outside the main gun body. I did not want to use excess force to pull the cylinder out. Is the cylinder suppose to slide out out of the main gun easily? Also if I replace the bumber and can not slide the cylinder out do I force the bumber through the bottom of the cylinder or top of the cylinder? Any tool recommendation for removing cylinder and bumber and reinstalling.

Robert

[rwbil]

The contents of these maintenance kits seems to be complete mystery. I can find no site that says exactly what is included. For 903789 / 60075 some sites say bumber included and other say order seperately. 90367 / 60030 I think is piston, gasket and bumber. Also say a 903756 / 60080, not sure what it contains. Does anyone know the exact breakdown of what is included in these kits. I do not want order a kit to find out the bumber or something else is not included.

Thanks,
Robert

[rwbil]

I was able to remove the piston, but now have an additional question. Everything looks to be good shape. The seal can slide up and down. If I slide it all the way up the part 127 cylinder space sits on top of the seal and blocks the air holes. Is that were it sits. Or maybe the design is such that at certain points it is suppose to block and at certain points it is suppose to be below the air holes. Any info would be appreciated. I think I am first just going to disassemble clean and regrease. Any suggestion of the right grease to use.

[DAVECAD]

As you may have already discovered, the Porter Cable FN 250A finish nailer is a huge POS!
I had shot approximately one hundred nails with mine when the Nose Cushion P/N 429 totally disintegrated. After about three hundred nails it would only fire once. I had to manually reset for each shot. Disassembled the gun and found that the Piston Bumper P/N 114 was a pile of crumbs. I don’t expect equipment to last forever but, with so little use? I would describe this as a “Toy”, not a “Tool”.

[UtahAV]

Sorry to hear that you have had such poor success with your gun. My experience with mine has been very different. I have owned a FN250a for around 10 years now and have had nothing but trouble free use. My gun is primarily used in a home woodshop but I have also installed trim in 3 basements, a family room and several bed rooms. It has not been used professionally by any means but it has definitely had some use. Out of curiosity, what brand of oil do you use when you lubricate the gun? That is the only thing I can think of that could cause the bumper to fail prematurely.

-UtahAV
-Mark

[retired1]

replaced all my bad seals along with the plastic piston stop, gun fired fine for about 30 nails then quit working. driver will fire once and then won't retract,pulling air hose off then manually pushing driver back there is air pressure against the driver so for some reason there is no air release after firing the gun, HELP any ideas