Hitachi ng90c2 won't fire , full gas and battery.it goes through the normal procedure but nothing happens when I press the trigger to fire a nail.

I presume the gun fires but no nail is ejected. A possibility is jammed nails in the magazine. Do you see a mark in your work piece of the driver blade? If yes then it is most likely jammed nails. If not could be a broken driver blade. If gun does not fire could be gas problem. (check in date, yes it does have a use by date), another cause of not firing is a broken wire particularly around trigger switch (switch is on trigger and hence the wires are flexing every time trigger is pressed). Another cause of not firing is a brass spring clip in handle assy if this breaks it stops the gun firing. Recently I have had more broken wires than anything else on these guns. Worth noting is that the Stanley Bostitch nail guns suffer the very same faults. Also note they are the same gun just different colours so you can fit Hitachi parts to the Bostitch and they are cheaper.

Does the motor start when you depress the nose against the work.
Look at the green light near the battery compartment it should flash one when you pull the trigger.
Is the gas in date?
Try warming the gas first by putting it in your pocket for 10 min before use.
You may also have an air leak, when was it serviced last?
Remove the head assy and reconnect to see if it is sparking when you depress the switches. Do not have the gas in whilst doing this.

This gun should be bump-fired only. Do not place the gun on the work and press trigger. Make sure that the safety spring is in place and has good tension. The spring helps to push the foot off the trigger so that it fires once. You could also adjust the screw that pushes on the firing valve. Turn in or out several turns till head of nail is correct when bump firing then lock the nut. The safety foot fits rather loose on the gun and should still work ok but can get so loose that it falls off the nose. Good luck

If the trigger is set to single fire, you will need to place the gun against the work then pull trigger as you have done. Try setting the trigger to bump fire and try again. If hear a thump inside the gun, remove the head and check that the head valve in not stuck from lack of lubrication. Easy test, remove the nails, remove trigger pin, remove trigger and manually push trigger firing valve. If the gun fires then suspect faulty trigger or safety arm not lifting enought to activate the trigger valve. Good luck

Check the date of the bottom of the gas. With the gas removed when you fire it you should hear a faint spark sound from the top. If gas is in date try putting it in your pocket for 10 minutes to warm it up. Open the front and make sure the piston is pushed all the way up into the machine.

If no air is leaking from the gun, take out the nails, remove trigger by removing 3mm hex head bolt to expose the trigger pin. With air connected and side door open so that you can see the feeder, quickly depress the trigger pin with finger. Gun should fire. If gun does not fire (only makes air sound at trigger) dissconnect airline, remove head and lube headvalve with white grease and reinstall. Test again. If ok replace trigger. If still no joy, replace trigger valve with new factory or generic (part # TVA6). If gun fires but does not activate the feeder claw, remove two 6mm hex bolts from front of gun and split apart upper and lower body and check white oring (part # 149885) Good luck

Trigger may be dirty, as an electrical switch the contacts can be intermittent. Also check to see if the safety plunger is set to correct depth and moving freely. Dirt can build up here......

Start with the basics:
First check that the butane (or whatever gas is used) canister is full. If empty, put in a new one.

Second check to make sure your battery is fully charged to be able to fire the spark to work the nail gun. If not get the battery charged and/or replaced as needed.

Third make sure all of the safeties are working properly and that you have them engaged to the piece of wood you are nailing when you try the trigger.

If beyond that it does not work it could be a bad trigger, a bad safety switch, or even a bad connection from the battery to the device.

get a senco