I am having the same issue with the exact same laptop. In my case, I've discovered that my problem is the left fan, which is not operating or spinning at all. The right fan was filling up with fluff due to having to pick up his brother's slack, and could barely spin itself it was so bogged down.
I discovered this by installing iStat Pro right after turning on the computer, and before it went back to sleep I did manage to get it to open- it reported right fan, many RPMs, left fan- 0.