When any moving part begins to stick, pour warm water on it. Again, beer is like glue when it dries. You need to soften up this beer glue prior to moving the part. This is due to inactivity and submersing the spout in the glass.
As to leak testing - faucet must be closed, keg tapped (coupler), and all the pressure valves in the open position. Note the high side pressure reading and close the cylinder wheel. If the needle drops slowly, you have a slow leak. If it takes a dive, you will get soap in your eye if you swab the leak!This procedure simply tells you that you have a leak. Slow or fast - you need to repair this or the low side reading will be all over the place.
Scott Zuhse, Instructor
Micro Matic Dispense Institute