Outdoor tap won't close completely
First try to grease the stem by opening the valve to max opening and smearing grease on the stem. Use special plumber's grease.

If that doesn't work, turn off the water and remove the service opening and and advance the stem all the way through the packing and apply plumber's grease to the stem where it seals against the packing. It may be necessary to apply a small amount of grease to the coarse threads inside the valve which advance and withdraw the stem, but I'm not sure about that. When putting it back in be sure to have the valve opened sufficiently so that the rubber seal is not pressed against the seat.