Blows air out the top of gun won,t pressurize to shoot a nail and can't get screw out of directional air port to inspect

Look for an O ring kit,,many times the firing cap seal splits thus loss of air

The allen screw/s that you mention are there to plug holes where automatic equipment would normally connect (such as automatic nailing machines) . This is only a plug and should not be driven in too far. I have also seen allen screws installed in the head to repair small crack/s.

Replace the O rings... sounds like its one in the firing valve ( rear cap of the gun behind the cylinder )

Most likely just needs piston oring. Remove nails from the gun and point nose of gun up then down again. If the piston travels up and down in the cylinder, replace the oring. The piston returns to top with air pressure and needs good snug piston oring and good lower bumper (if bumper is cracked or missing pieces ~ replace ). Be sure to lube the orings in the headvalve with silicone paste or white grease. Part # ORK11 oring kit will reseal the gun. Good luck with your repair.

Stop using it and take it in for service. If it is leaking air then an o-ring or seal may have failed (most likely guess) and it needs to be replaced.

If every nail is stopping at the exact same height, a likely reason is the tip of the driver is broken off so it's not long enought to drive the nails all the way to flush. If the height of the nails is slightly different you may have worn or broken o-ring(s) inside the gun and air is leaking around the driver's piston or elsewhere in the gun so that the driver isn't getting full pressure. You can take the gun apart and inspect the o-rings. If you push the driver all the way down the tip should come flush or slightly past the end of the nose piece (not the safety tip). Parts are easy to find online or at a service center if you have one nearby.

A new trigger valve and o-ring kit will give you a like new gun. Just remember to replace all available o-rings in the kit, lightly grease all of them as you reassemble the gun and use pneumatic oil at the beginning of the day so you won't be doing it again in a couple months.

The o ring inside the top of the gun is worn. This is a part you can order through an authorized dealer, OR you can take that o ring with you to your favorite big box store and find a 5pack of the same size for about 1/4 of the price! Just unscrew the screws on top of the gun and the top will come off exposing that o ring- it may be in pieces. if there isn't enough of it left to take with you, you can take a measurement.

Not sure exactly what Bostitch framer model you have, but if it is powered by compressed air, as long as you remove the air hose from the nail gun, there should be no risk of the nail gun firing while you remove the jammed nail. There should be a way to access the driver area from the top of the nail gun, even via a latch or a couple screws. Remove the top part of the driver area and that should give you access to the jammed nail, which you can remove. Use long nose pliers or something similar if the nails are really stuck.

Set up the pressure on the air compressor. First plug the air compressor in, then check the pressure. It should be between 90 and 110 pounds per square inch (PSI) for home use. If it is not in this range, turn the knob to the left to decrease the pressure and to the right to increase the pressure. Use the appropriate nail gun for the job. For example, to nail shoe molding to base boards, a standard finishing nail gun would be perfect. It holds any size nail between 5/8 inch and 2 inches. This nail gun could be used for many projects with great results. Check the gauge the nail gun takes before purchasing the nails for the gun. If you get the wrong gauge they will not fit in the gun. You can check this by looking at the information printed on the side of the nail gun next to the model number. You can also open the nail chamber for this information. Attach the nail gun to the air compressor. You can do this before or after you load the nails into the gun. Use the air compressor hose to attach to the bottom of the nail gun. It screws on much like the end of a hose. If you do not have the right size air hose, you can find one at your local hardware store.