My Hitachi NV45AB is leaking air from the trigger air valve. The gun still works if I just keep the trigger depressed and just smack the tip into the shingle.

SOURCE: my hitachi nail gun NR90gc2 will not fire

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.

SOURCE: i took apart and replaced

If orings fit too tight cylinder will not move against the headvalve seal (headvalve is the black rubber or vinyl seat in the head). To help the cylinder reset, bump the head against rubber matt. If the cylinder resets, good to go, if however the cylinder does not move into position, remove the head and check that cylinder moves up/down about 1/4 inch. If it does not move pull cylinder and use 400 grit sandpaper on cylinder where orings contact. Remove all scratches and reinstall. Good holidays

SOURCE: When I depress the trigger

INTERNAL O RING IS SHOT

SOURCE: Air leaks thru exaust on

Examine exhaust tube under valve for cracks and make sure that the tube seals correctly against body of the gun with rubber gasket. If tube is ok and has rubber gasket in place, check for correct cylinder movement. Press down cylinder with thumbs, the cylinder should return. If it stays down, pull it back up. If it is very hard to pull up, cylinder orings too tight or body of gun is warped. If it comes up with light to firm pull, go ahead and reinstall the head and test. If air leaks, try bumping the head of the gun (with air connected) against firm rubber to reset the cylinder against headvalve. If it still leaks, suspect that the cylinder is not moving up against the headvalve due to tight fit. Remove the cylinder and sand surfaces where orings contact to remove fine scratches with 400 grit paper. Also stretch the spring below the cylinder a bit to exert more pressue. Lube the cylinder with silicone paste lube. If you suspect warped body, remove all the orings from middle section the gun and insert the cylinder into body looking for out of round (with no orings the cylinder should just slide in to body of gun easily). Good luck

SOURCE: I have a Hitachi coil

I dont recall that there are any orings in the head area. Large leak from head area is caused by cylinder not retracting and seating against headvave. Small leak is usually gaskets between headvalve or cracked tube above headvale or rubber tube seal not seating against body of the gun. Test cylinder movement. Remove the head and push down cylinder, the cylinder should retract. If the cylinder is already down, pull it up. If the cylinder is very hard to pull up, most likely orings too tight or body of gun is warped. If the cylinder moves up with just little force, reinstall head and retest. If small leak, remove head and remove headvalve and look very closely for cracks in the head and tubes.