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Stuck driver hitachi roof coil gun. how to fix?

HitachiNV 45AE roof coil gun stuck driver or piston, How do I fix?

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Disconnect the air. Can't stress this enough.

Turn it upside down and find the bottom of the piston. Use a punch or a short piece of solid rod and gently tap the piston back to the home position. You may have to pry and/or pull out a mangled nail in the process.

After this, be sure to put some oil in the intake as this is one common cause of jams like this.

If it's an older nailer, then it probably was built for a different angle on the nails than what is currently available. I have one like this. It will do fine 99.9% of the time with 1 1/4" nails but does very poorly with longer ones. There is really nothing you can do about this unless you find some old nails. If you can find hot dip nails they seem to do better than electro-galvanized as well - they also last better but are more expensive.

Posted on Jul 12, 2009


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3 Answers

Why does my roofing nail gun jamming, it would fire one nail and the hammer will remain out, so i toke a screw driver and push the hammer back in, and it still did the same thing

Simple test for piston jam. With nails removed and latch open, point nose of gun up then down. If the driver slides up and down in the cylinder as you move the gun, replace the piston oring (test gun for proper operation). If the piston stays in the upper most position as you move gun (push driver to top position), check lower bumper and bottom seal under the bumper (sheet). Replace as needed. If the lower parts are in good condition (good piston oring, lower bumper and sheet) , replace the 3 orings on the feeder piston. Good luck

Dec 03, 2011 | Hitachi NV45AB2S Coil Roofing Nailer

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My hitachi nv45ab2 roofing coil nailer misfires and only shoots every third nail

Hitachi coil roofing nailer will skip nails if the piston oring is worn, the feed spring is weak or lower bumper is cracked. Easy to check. Remove nails and air supply. With side door open point nose of gun up then down again. If the piston moves up and down in the cylinder, replace the piston oring. If piston does not move and is in the up position, check the feed spring for tension. With air supply removed and door open, slide feeder back and press on feeder from door side to check tension. It should spring back to position against rails.If is feels loose, replace spring and retainer pin if the pin is worn. If piston oring is good, and the feeder has good spring tension, suspect lower bumper and the plastic part below the bumper called the "sheet". Remove head and pull the cylinder to examine lower bumper. Parts are available at Good luck with your repair

Aug 09, 2011 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Nailer makes a small clap noise and will not shot nails

When the driver or headvalve is stuck in place and the gun is fired, there will be a pop sound or the sound of air being released within the gun and at the trigger. Remove the nails and air supply insert metal rod into nose of gun forcing the driver against headvalve (a couple of firm taps will do). Retest gun. If no joy, remove the head being carefull with head gasket. The driver should be at the top positon (if driver drops to bottom of cylinder replace oring). Pull the driver and lube the piston oring seal. Headvalve should move in with thumb pressure, if stuck, remove and clean / lube orings. Replace parts as needed if scratched, cracked or generally worn. Use plenty of silicone paste lube on orings ( sold at Lowes in the plumbing department and swimming pool supply stores). Good luck

Jun 04, 2011 | Dewalt D51321 3/4" 1 3/4" Heavy Duty Coil...

1 Answer


For piston to retract properly, the bumper and small sheet below bumper must be intact. Also the piston oring should just hold the weight of the piston at the top of cylinder (not too tight). Remove head and pull out cylinder. Look at bumper and make sure that it is not cracked or missing pieces. The part called the "sheet" should fit snuggly on the driver and not allow the driver to be removed from top. To replace the sheet, you must remove nose of gun. Good luck

Feb 02, 2011 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

My new (used once) hitachi roofing nailer wont feed.when I hand feed it,it has no power.Like theres no air pressure.....Yes the compressor is on. any ideas?

Remove nails and disconnect airline. Open door latch and check for back and forth movement of the feed piston. It should move with little force and should have spring tension when you push on the leading edge of the feeder. If very hard to move then most likely orings are swollen or stuck from lack of lubrication or water entering gun. Remove head being carefull not to tear gasket and check piston/ oring for tight fit( the piston will not come all the way out, just enough to repalce oring). If very tight then all orings should be replaced. If just dry, lube with silicone paste or proper oil. Check that the cylinder retracts into body of gun and rather easily pulls back up. Do not use pliers on the the cylinder; it is spring loaded and shuld move with finger pressure. Parts are available at Good holidays

Dec 28, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Hitachi roofing nailer leaks air out the back after falling off roof, I have 5 of them all with the same problem. any ideas?

SOLVED! I replaced all the o rings put it together and air jus blew out the exhaust port. I made the mistake of pushing Piston plunger cylinder into the gun till it seated. this left a gap between the head and cylinder. I took the gun apart, removed the cylinder, an reinstalled it only far enough to seat past the o ring gasket. I then installed the head and let the head seat the cylinder as I tightened the screws. this worked on two guns with the same problem. Jn 3:17

Dec 11, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

The nailer piston on my hitachi roof gun stays out and will only fire 1 out of 15 times. i've tried oiling it, and hear no gasket leaks. what could it be ? dan.......

There are o-rings in the gun that route air around the cylinder to push the driver back up. One or more of these o-rings are worn or broken. You can get it fixed at a service center or you can go to sites like to find a breakdown of your gun and order the parts. Unfortunately Hitachi doesn't make all in one repair kits and if you replace one, replace all of the o-rings.

Sep 13, 2010 | Hitachi 1 - 3/4" Coil Roofing Nailer

1 Answer

When I connect my gun to air, it is stuck in the exhaust phase. The piston advances whether I pull the trigger or not, and it continues to exhaust. It does not reset.

Hitachi is one of the very few nailers that does not have the firing valve in the head. Instead the cylinder moves within the body of the gun. When the cylinder retracts it rests on the headcap (Rubber seal). If the cylinder gets stuck in the down position, lightly taping on the head will sometimes reset cyl against headcap. If the cylinder orings/contact surfaces are dry/dirty, the retraction spring will not have enough power to reset. Also, if the headcap rubber is cracked or worn the cylinder cannot make a good seal and leak as you describe. Remove the head being carefull not to tear the gasket and examine headcap and replace as necessary. If headcap looks good, pull cylinder and clean all surfaces where orings contact and remove scratches with fine sandpaper (400 grit). Lube orings with silicone paste lube available at Lowes in the plumbing department and/or swiming pool supplies area. Generally, you do not have to replace any orings unless they are broken or badly worn by grit. After you reinstall the cylinder, make sure that it moves up and down (travel is about 1/4"). Piston oring should fit snug enough to hold piston in place without dropping down the cylinder under its own weight. Parts available at Good luck and post again if you have other questions.

Aug 14, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Hi, i got a hitachi nv45ab and My nailer leaks air out the back

Hitachi nv45 series is the most popular line of nailers amoung professional roofers. There are three areas that develop leakes. Leak out head vent indicates cylinder stuck in lower position or headvalve worn. With air connected, gently rap head of gun against rubber mat to move cylinder to position. (Use caution not to damage head). If this action works, gun needs cleaning internally or lack of oil. If air still leaks out vent remove head and examine valve in head and replace as needed. Check that cylinder moves freely up/down (travel aprox 1/4"). If cylinder is hard to move pull cylinder and clean replacing orings as needed. If leaking around trigger, remove rollpin and trigger and check nylon ball for pits and replace as needed. If leaking around base of gun check for loose bolts and/or worn gaskets. Remove nail canaster to check feed piston gasket and screws. Good luck with your repair and post again if you have other question.

Aug 04, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

My brand new hitachi NV45AB2 roofing nailer leaks air through the trigger when it is half depressed. I purchased one and returned it only to find the new one I recieved to replace it does the same thing....

Take off the back cover and make sure it's not too dry inside. Spray the inside with some WD40. You can take off the top cover. Pop the piston, cylinder, and head valve out, making sure all the seals and rings are seated correctly.Sounds like the piston is momentarily sticking. Does it shoot at all? Lemme know. Please rate me

Jun 03, 2009 | Hitachi NV45AB2 Roofing Coil Nailer

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