I had this same issue.. what I done was unplug everything from the back of the x box and then take the top of the xbox casing off ( i suggest you watch a video to do it) .. once it was off I left the wire on that connects the front of the xbox to the touch buttons on the front and I plugged my power lead back in and the HDMI cable back in (while the top of the casing was still off) and then blowed my fan a couple of times to move it arround and then hit the on button on the front of the x box (with the casing still off) and then blowed the fan a bit to get it moving and then it come on…..
hope this helps someone