This is Windows 7 with python 2.7
I have a scrapy project in a directory called caps (this is where scrapy.cfg is)
My spider is located in caps\\caps\\spiders\\c
In my case, i set 'LOG_STDOUT=True', and scrapyd can not return the results to json response when you are looking for your spiders with '/listspiders.json'. And instead of that, the results are being printed to the log files you set at scrapyd's default_scrapyd.conf file. So, I changed the settings as this, and it worked well.
LOG_STDOUT = False