Diplomat dishwasher - no water from top and bottom sprayers?

Hi, long shot - machine going through full cycle but not properly cleaning dishes. Seems that no water is coming from top or bottom spray arms - but does appear to be coming from middle one? Inlet valve fully open, no obvious leaks or blockages as far as i can tell. has recently been making a sort of grinding sound? is it likely to be totally defunct / need new pump or whatever? any ideas ?