Maybe I've missed a setting somewhere, but when I search on a phrase that I know exists on the site, I get a "not found". It looks to me as though the search is concatenating the words and skipping the spaces.
So if searching on "word1 word2" (with or without the quotes), the page returned says
Not found word1word2 in your blogs.
A search on either word1 or word2 is successful.