DeWalt D51257 has been lightly used for home projects but it stopped working. When trigger is pulled, only air is coming out (through the trigger area) but no nail is fired. Should I replace the trigger valve? Cylinder and o-rings looks ok. Thanks for any advice.

  • Checked, found nothing blocking... one thing I noticed was when I engage the safety lock, I can hear small amount of air leaking there.
    – user74219
    Aug 12, 2017 at 15:25
  • 1
    Did you open the front to expose the drive pin to see if it is retracted entirely? If it does not retract entirely it will leak air when the trigger is pulled. I have had nails jam behind it and keep it from retracting and had to pull it up by hand exposing the nail behind it. Disconnect the air before doing so.
    – Jack
    Aug 12, 2017 at 21:26
  • Thank you very much for your thought. I opened the top and took out the cylinder and the piston. I don't think there was a nail stuck inside. I suspect the O-rings are bad?
    – user74219
    Aug 14, 2017 at 16:47

2 Answers 2


Same problem with my D51257. Used about 10 years ago and when I tried to nail this past weekend shot two nails and stopped. Problem was the trigger valve, three O-Rings are gum type rubber and over time these dry out and disintegrate just like a gum rubber band. I ordered a replacement trigger valve from Amazon and will replace the valve in a few days. In the meantime, I went to Ace Hardware and bought three O-Rings and after sanding the trigger shaft O-Rings down to fit in the trigger cylinder, I reinstalled the trigger and nailer works fine. Will keep new trigger on hand for future use.

  • You should seal up the replacement ring with multiple air-tight bags or it'll just dry out before you get to use it.
    – Nelson
    Jun 21, 2023 at 5:02

I had this issue on a Makita siding nailer. 1 week old, was working perfectly the day before. Checked that the piston wasn’t stuck, opened it to see if residue was affecting the o-ring; everything was fine. In frustration, I held the trigger down while pressing the nozzle against the material. After about 5 seconds the gun finally engaged. Working perfectly again.

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