Leaking air through trigger area. Will not nail at all.

The trigger valve should release air when depressed. This release of air comes from behind the head valve. If the head valve does not pup-up when the trigger is depressed then air is leaking past the head valve orings. Try coating the head valve orings with plenty of white grease and retest. If the gun fires you know that orings are leaking. Test with no more than 100 psi. Good luck with your repair.

You will have to take the gun apart and change the rubber o-ring gasket for the trigger mechanism..Go to a Home Depot or other contractor outlet to get parts or info...The gasket actually keeps the air from leaking so it will nail.

Remove the nails and take off the trigger to expose the trigger valve (usually part # tva6). Connect air and spray soapy water on the valve to determine if the air is leaking from the center of the valve or around the outer edge between the body and valve. If leaking from the center, could be defective valve or debris under oring. Pop out the valve and examine internal parts for cut oring or defect. If leaking from between body, you could have cut orings installing the valve. Make sure that there are no rough edges in the body of the gun. Bump fire or single fire happens with the trigger type not the valve. Bump fire trigger is usually black metal and single fire trigger is light color plastic. Good luck

Leak around trigger could be trigger valve internal orings or orings on the outside of the trigger valve making contact against the body of the gun. Spray soapy water to determine where the air is leaking from. If air is leaking around the outside of the valve, most likely the orings were cut upon installation of the valve. If leaking from internal valve, most likely worn or broken oring; easy to fix if you have a source for orings.

To remove the trigger valve for service or inspection (take close-up photo of trigger area for reference ):
disconnect airline, remove nails, remove trigger retainer pin, remove trigger, remove roll pin /s holding trigger valve in place (use 3mm punch to remove retainer roll pins which are located in the body of the gun just above the trigger valve). With retainer pin/s removed and with gloved hand (under trigger valve), apply air pressure to gun to blow out the trigger valve (use lower pressure to push out trigger valve because it could come out with force.). With trigger valve in hand notice that there are two slots or groove cut neer top of the valve where the retainer pins rest, you will need to reinstall valve into body with slots aligned to retainer pins. Remove retainer pins holding trigger together to pull out internal valve. Good luck and post again if your have other question about the trigger valve.

Air leaking around the trigger area could be caused by vinyl ball / gasket under trigger valve bushing or orings within the gun. Easy test, remove nails and connect air (assuming that air is now leaking around the trigger area). Depressing the trigger stops the leak, replace vinyl ball. Depressing trigger does not stop leak, move plunger b (plunger B, small shaft under bubber bushing next to the trigger valve) with your finger in then out to determine if air leak changes tone. If air leak changes sound or tone, then air is leaking past orings of the cylinder guide and/or cylinder plate and/ or the cylinder itself is scratched by debris where the orings make contact. Pull out the cylinder and examine the contact areas. If scratched, use 300 grit paper to smooth, if smooth, however, suspect the orings of cylinder guide (or cylinder guide is cracked). The cylinder guide is difficult to remove and install without causing damage to guide or cutting new orings when installing. Do not remove the guide unless all the other options have been checked. One last bit if information, I have noticed that some guns will leak air if the orings on the feeder piston do not fit snuggly. Make sure that leaking sound is not coming from feeder area (remove the basket and feeder/feeder pin/spring and pull out the feed piston, making sure that the largest oring is making good contact within the cylinder). Good luck with repair.

the trigger assembly would need replaced. I have detailed instructions in the tip section on the removal and installation of the trigger valve. Let me know if you still need more assistance.

Remove the nails and air supply. With side door open notice position of driver. Driver should be at top position with tip not visible. If driver is down and it moves within cylinder when you tilt nose up then down again, time to replace orings. If driver is down, it should extend past the nose about 1/4 inch (if driver is broken at the tip the end will look rough and nail will not drive in all the way). If driver extends past the nose more than 1/4 inch then lower bumper may be breaking up /cracked. Easy test for proper function. With nails removed and side door open, connect air to gun and dry fire gun against hard rubber or old coiled air-hose (with air connected and trigger depressed, no air should leak from trigger area, if air leaks when trigger is depressed, look for fault at trigger pin). Feeder should move back then forward in quick motion almost matching speed of driver and driver should not creep down between shots. No air should leak from nose of the gun (push nose against hard rubber and depress trigger and hold in this position, driver should stay down with very little or no air leaking out of nose, when you release trigger, driver will return). If air leaks out of nose while holding in this position, replace lower bumper. If a quantity of air leaks from valve in front of trigger, cylinder orings may need replacing or outer part of cylinder has fine scratches (remove scratches with 400 grit paper). Parts are available at www.toolpartsdirect.com. Good lucki

A nail gun works on compressed air.
When you hook the air hose to the gun it fills a cylinder with air pressure.
When you pull the trigger. the cylinder pressure is released onto a firing pin that shoots the nail.
The air pressure line is also connected to the trigger and therefore the trigger has to be sealed.

When ever using a nail gun, you add a bit of gun oil in the back of the gun (not 3-in-1motor oil, it has to be non-detergent gun oil)

If you haven't used the gun in a while, it is best to oil up the gun and let the oil run down into the gun.
If you use anything but gun oil, the seals will give out.

Your trigger seal has given out. It is probably an 'O' ring. You can access it by taking it apart. Look for the O ring.
Bostich makes re-build kits for the different guns that you can buy on-line.
Back when I was in construction, there were several nail gun shops that sold and serviced nail guns, and sold nails to the contractors. I don't know if that business model is still active or if you have to send the guns to Bostich service center.

There are O-ring seals around the trigger that are probably leaking. You can try to lubricate the gun by adding the pneumatic oil to the air supply. That may be enough to seal it back up. Otherwise the seals and/or the trigger assembly will need to be replaced.

Dan

To fix this problem you will have to disassemble the gun to get at the trigger area. Look for a broken "O"-ring. This is probably jamming the recoil of the drive pin.