Airgun Technologies Air saber

No Air Saber but always suspect the one-way valve of air reservoir if any of my PCPs stop taking air after they've been successfully doing so. First, I'd verify air fill source is working by doing pressure check with pictured test plug or by filling another PCP. If air source checks out, I'd put a drop, or two, of heavy-weight silicone oil (like used for treadmill exercise machine) in foster fitting or in end of fully inserted fill probe and let sit. If one-way valve remains stuck with corrosion or debris, disassembly might be required,
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after assuring air reservoir is unpressurized. WM