I recently took my mid 2009 macbook pro apart to clean some coffee spillage. The computer worked fine even days after the incident, but the keys were beggining to get sticky, so I decided to clean it. After re-assembling the computer, I discovered it would not boot from the internal drive, but it would boot from the same drive connected externally (via usb).
However I can get it to boot using the internal drive, after removing most of the screws attaching the bottom lid to the unibody. Once tightened back up it will not boot from the internal. I have already tried multiple bootable drives, with the same conclusion.
I'm guessing the screws are sorting the drive out. Has anyone else had this problem.
Try booting lid on, in Verbose mode. Hold down CMD V
Then watch as it lists on the s Rene what is happening. Then take note (I take pictures) of what is the last thing it does, where it crashes or stops.
Could it be coffee in the SATA cable, that is sort of on one side of the connector so that when lid is on that side is the only one pressing and making copper contact. Looooong shot this one
Check the ifixit.com repair manual to see all the wires and where they are located so you know where to look inside for pressure points