Indesit WI121 program selector keeps clicking round when I switch the machi?

Indesit WI121 washing machine. Sometimes when I switch the machine on, after it's taken in some water, instead of pumping a small amount out then proceeding with the selected program, the program selector just keeps clicking round with the pump running all the time. I;ve tried the cure in the manual (switch off, select a program stop point then switch on again) but this doesn't work.