Trigger problems When I pull the trigger air leaks out of the trigger but the gun will not fire. Do you replace the trigger assembly or just the o-rings

I have repaird hundreds of nail guns with a problem similar to yours. Depending on the brand and model, the problem can be repaired by checking the following. Headvalve orings should be checked for wear and any surface that the orings contact must be smooth and free from scratches. If the surfaces are scratched try to smooth with fine sandpaper and use light grease instead of oil when assembling. The safety contact foot may not be reaching high enough into the trigger to properly push in the trigger button. Check for worn spots on the trigger that may be filled in with epoxy, loose fitting trigger caused by worn roll pin or retaining pin. Some of the trigger valves as used on many bostitch nailers (tva6 valve) used a plastic pin which contacts the trigger. If this pin is loose or worn the valve should be replaced. Some tva6 valves have a vinyl looking sort of oring that fits too loose on the spool. This vinyl oring in not available by itself but if the oring fits too loose the gun will not fire and leak air. On bostitch remove the trigger and the rollpins holding the trigger valve and apply air to gun to eject valve. (use heavy glove to catch valve as it will come out with force)

Usually they come in assy