Carpet shampoo system

Question

When using the carpet shampoo system and moving the Kirby back and forth, only a narrow stream of water with very little foam comes out onto the carpet. I have the suds control valve all the way to the left but no luck. No suds is dispensed in the tray when the Kirby is pulled backwards. I used a whole tank of shampoo and didn't even clean a 9x10 carpet. Any ideas? Thanks a million. I am borrowing my friend's Kirby and she is not home to ask!
Joyce