I have a 18v dewalt finish nailer the motor comes on when i press the trigger but it wont fire a nail any ideas why

Could be lack of lubricant or safety foot not pushing trigger valve pin all the way in. Easy to check. Remove nails and remove trigger to expose the trigger valve firing pin. Connect air and with very quick action depress the firing pin all the way in with finger. If gun fires adjust safety so it pushes on trigger pin completely. If no fire, remove head and head valve and apply plenty of white grease or silicone paste to orings and reassemble for retest. Good luck

A few things to check - some may seem overly obvious but humor me:
1) Check your nails - make sure they are the correct angle and gauge
2) Check to make sure there is not a piece of a broken nail in the nose
3) Check the driver blade & insure it is not bent or chipped
4) Make sure the nail carrier spring is pushing nails forward and isn't getting hung up

It sounds like the battery has a low charge or is defective, have it tested.

Dewalt has two triggers available for their framing nailer. The black trigger (390746-00) is a bump style trigger. While holding the trigger, you will be able to fire a nail by pressing nose against work. This trigger is preferred by most framers because it is much faster. Gray trigger will only allow one nail to be fired. Bumping will not work with the gray trigger. With trigger released, you must place the nose against work then pull trigger to fire. To fire next round, you must release trigger, pull gun off the work, again place nose against work then press trigger. Check dewalt web site for recall information. Some dewalt framers have been recalled for faulty trigger. Good luck with your projects.

It may already have a nail jammed in it. You may have to take off the front face that holds the firing pin. There should be one or two screws in front just above where the nails come out. If you remove these there will be a plate that comes off and then you can remove a jammed nail. Look first to see if there is a jam before doing this. Also maybe you have the wrong guage nails or maybe you don't have proper air pressure. Hope this helps.

Hello, W/D here.

The better way is to disconnect the air line from the gun, and place several drops of light oil in the gun while holding the trigger down. Oil daily. Then, re-connect the hose, and fire a few nails into scrap wood.
Another trick is to spray your nails with WD-40 before you load them into the gun.
Best regards, --W/D--

You could have a nail jammed. Remove the front assem. where the nails come out and see if somthings stuck like a nail.

The driver is probably stuck. The manual tells you how to access the front of the device. Check there (I have also had several hard to find jams) - be sure to remove all nails first.

The driver is silver in color, so it's easy to see if it's jammed. Use a slotted screwdriver to push it back up. I have had this happen more than a few times.

Check whether the trigger is working properly, and whether the air valve is not leaking.