If the air stays in as long as the pump is attached then it sounds like the valve stem. Maybe your friend will let you try his valve stem with your bike.
Those that have had their shock fail have had oil leak from it.
2013 XC Suede Nuclear Sunset
21" Conversion incl. ABS Module, Rear Shock and Forks
Lloydz HPT Cams
Lloydz Air Filter
Lloydz Timing Gear +4
31 Tooth Drive Pulley
Southern Motorworx Tune: 118.08 HP - 114.97 Torque (before 31 tooth drive pulley)