Posted: 26/04/2012 at 21:32
Position sounds fine and the plant healthy so, unless you bought it in flower, it's likely to be too young. Some wisterias are seed grown, and they can take up to seven years to flower.
The other point is have you pruned it correctly - look here for instructions:
http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=242