Is it possible that all the coyotes have been removed from the area? Or is it possible that there are so many gut piles that they haven't gotten to yours yet? I have the same situation at my place. I put a deer carcass out in front of one of my deer cameras in hopes of recording a coyote on it. No luck after a week.
Here is all I have found on the carcass:
http://youtube.com/watch?v=eInnD18gv88