Campsis

[NOISETTE]

Hi I have4 campsis which I bought about 4 years ago. None of them have flowered although the foliage has grown profusely. Anyone have any hints as to why there are no flowers

[Robinia]

Where are you, is it a mild area? They need as much warmth and sunshine as possible so the stems ripen and go woody before they'll flower.

[Chipchopper]

Robinia is right, they do like a warm sunny aspect to do well, plus shelter from strong winds will also benefit them.
You could try sprinkling a general purpose fertilizer around the root area.