Get his teeth and mouth checked by the vet. If this is fine try splitting his food into two or three smaller meals. Leave the food down for fifteen minutes and then remove it whether he has eaten it or not. Do not feed him any other food until his next meal. He will eat when he realises that he gets no extra attention or food for this behaviour.
Do you feed him outside in the summer? Maybe the dogs you spoke off in another post are harassing him and making him feel too uncomfortable to eat. Try feeding him inside.
Has your Mum called animal control yet?

[This message has been edited by carrie (edited November 06, 2000).]