Craftsman 875188020 air leaks out the side only when trigger is pressed.

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.

Two areas to check when air leaks from around the trigger. Rubber ball under trigger pin will cause air to leak, however when good side of the ball falls on the seat, air will not leak for a while. If air is leaking from plunger pin (just in fromt of the trigger pin), remove the head and pull out the cylinder plate to reveal broken oring (oring part # 876161). Good luck with your repair project.

Assuming no air leaks when airline is connected. This condition is caused by either restriction within the headvalve /upper bumper and or trigger valve worn/dirty. Easy fix however. Remove the head and pull the headvalve. Examine the upper bumper for cracks/splitting. Replace parts as needed. Lube with silicone paste lube and retest. If condition remains replace the trigger valve. Good luck

Air leaking from trigger when trying to nail indicates that the headvalve is stuck or headvalve orings are dry and allowing air to pass. Remove the head and pull out the headvalve piston. Examine orings for cuts or broken (replace as needed if orings worn and cannot make seal). If headvalve was stuck/dry, lube with plenty of silicone paste lube (sold at Lowes in the plumbing dept. ). Should be good to go. Good luck

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

first I hope that you drain the water out of the tank regularly. It seems as though you might have an air hose collapsing but in any case there is something apparently restricting air flow too the gun. try opening the petcock and see if you have steady air discharge or not and if you have another air hose try it. Also, are coming directly off the compressor to the tool or do you have an oiler or drier in line? if so, eliminate the accessory. Let me know how you do....I'm curious.

its just stuck up try putting in a drop of oil first

The fix it replace the trigger valve. It is a 5 minute job and seems to be a pretty common problem. Bad news is they seem to run about $30. I believe the bostitch # is TVA6

check to make sure that there is not a nail jam , if the driver will not retract then the gun will not cycle . if no nail jam then replace the inner trigger

The seal is bad inside leaking air pressure to the gun without squeezing the triger. Get a reseal kit from Sears