My sister had the same problem with wisteria and it turned out she was feeding it which wasn't necessary. The year after she stopped, it flowered and continued to flower each year.

All jasmine plants prefer sun to light shade sites with well-draining and moderately fertile soil. West facing wall? I don't think it gets enough sun.

It needs the strong afternoon sun; evening sun is too weak for jasmine.

Is it in a pot or in the ground? Do you, or have you, ever pruned it and if so, when? When you say 'summer Jasmine' do you mean Jasmine officinale or another form of Jasmine?