Nailer: Won't Fire

A blown seal inside the nail gun will allow air to escape dropping the air pressure inside the nail gun. If bad enough it will not allow the nails to fire. To check the seal to see if it is bad, remove the top cap and pull out the cylinder. Remove the bulk head. Examine all the seals for signs of deterioration or damage. Replace any seals and reinstall the cylinder back into the housing. Install a new gasket with the top piece and tighten each screw a small amount at a time to seat the gasket.

A broken spring inside the head valve located inside the top cap will impact the operation of the nail gun firing nails. To inspect the spring, remove the top cap and pull out the head valve and inspect the spring. If the spring is broken install a new one. Reinsert the head valve and install a new gasket with the top cap and tighten the screws a little at a time to seat the gasket properly.

The piston head valve controls the air flow into the cylinder chamber forcing the piston/driver assembly down. If it is malfunctioning it can prevent the nail gun from firing. Remove the top cap from the nail gun. Use a pick to pull out the piston head valve from the cap. Examine the piston head valve for any signs of wear or damage such as worn out O rings, cracks in the piston head valve or anything else out of the ordinary. Install a new piston head valve if it is needed. Clean out the housing. Apply a small amount of Vaseline or lube to the O rings before installing. Reattach the top cap with a new gasket and tighten the screws in an alternating pattern a little at a time to seat the seal.

The O rings are placed around the cylinder and the housing to prevent air from leaking. When an O ring fails it can impact the operation of the nailer, one of them being, preventing the nail gun from firing due to a lack of air pressure. When replacing an O ring it is best to purchase an O ring kit and replace all the O rings at the same since you will have it all apart. The kits are inexpensive and if 1 O ring has failed it usually isn’t too long before others follow.

To examine the condition of your O rings remove the top cap off from the nail gun, the magazine and the bottom nose piece. Pull the cylinder out of the nail gun, you may have to tap on the body with a rubber mallet to free it. Remove the piston/driver assembly from the cylinder. Remove the metal ring from the housing that supports the cylinder inside the gun. Examine the O rings around the outside of the cylinder, and the metal ring that supports the cylinder for tears, rips, and signs of deterioration.

Replace any damaged O rings (or all the O rings if you are rebuilding it). Remove them by placing a small screw driver under them and lifting up and walking them off. Install the new O rings and apply a little grease or Vaseline to the O ring. Remove the piston head valve from inside the top cap and inspect and replace and damaged O rings. (On some models it separates into 2 pieces. Separate the inside portion of the valve from the outside portion by pulling them apart. Examine the O rings located on the outside and the one on the inside. Replace these O rings. Reassemble the valve).

Reinstall into the head. Install the piston/driver assembly back into the cylinder. Slide the metal ring over the cylinder assembly. Make sure the piston is all the way down in the cylinder for easier installation into the housing. Install the cylinder assembly into the housing. Make sure the driver is aligned properly to the opening in the housing and press the assembly into place. Install the top cap with a new gasket, magazine and the bottom nose piece with a new gasket and tighten the bolts a little at a time in an alternating pattern to seat the gaskets properly on the top cap and bottom nose piece.

The bumper and spring assembly dampens the recoil of the driver and returns it back to the top to strike the next nail. If the bumper is worn and failing then the driver will snap down below the nail and will not be able to pick it up. To replace a worn out bumper remove the top cap from the nail gun and remove the piston/driver assembly from the cylinder. Pull out the bumper and install a new bumper if the old one is broken, worn out, disintegrated or any thing else that does not look normal. Reinstall the piston/driver assembly back into the cylinder and reattach the top cap and tighten the screws in an alternating pattern a little at a time to seat the seal.

The piston ring seals the chamber and prevents air from blowing between the piston and the cylinder wall. If this ring fails there will be inadequate air pressure and the nail gun will not fire or fire very weakly. To inspect and replace the piston ring remove the top cap and remove the piston/driver assembly from the cylinder. Inspect he piston ring for tears, cracks or anything else out of the ordinary that will allow air to leak by. Remove the piston ring by using a small flat blade screw driver and prying under and up then walk it off the piston. Install a new piston ring, apply a little lube or Vaseline and reinstall into the cylinder aligning the driver with the opening at the bottom of the cylinder. Reattach the top cap with a new gasket and tighten the screws a little at a time in an alternating pattern to seat the gasket.

The trigger valve controls the flow of compressed air which controls the piston/driver assembly. When the trigger is pulled it releases air forcing the piston/driver assembly down and on some models controls the air forcing it back up. If the trigger valve is leaking air it can cause it not to fire as there will be a loss of air pressure. To replace the trigger valve remove the magazine. Remove the grommet on the side of the trigger and drive the pin or pins out. Remove the trigger. Some trigger valves are threaded into the housing and some are held in place with roll pins. Use a wrench or tap the pins out depending on your model to remove the valve. Clean out the inside. Apply a very small amount of Vaseline to the O rings. Install the new trigger valve and reassemble. Reattach the magazine.

The piston/driver assembly is placed inside a cylinder and is a one piece unit. If your nail gun won’t fire the driver could be bent and jammed inside the nail gun preventing it from firing. To examine the driver for damage lift the quick release and examine the driver. On some models you may have to take it all apart to get a better view of the driver. To access the piston/driver assembly remove the top cap on the nail gun and remove the cylinder and driver assembly. Tap the housing with a rubber mallet to free it up if needed. Remove the piston/driver assembly from the cylinder. If the driver is bent it may be difficult to remove. Install a new piston/driver assembly into the cylinder if it is bent or damaged, apply a small amount of Vaseline or lube to the piston ring. Install the cylinder back into the housing and reattach the top cap. Tighten the screws in an alternating pattern a little at a time to seat the seal properly.