Lets give this a try put the drive back into the system using the HD bay or optical drive bay. Now this time when you start your system press and hold the Option key to get to the Boot manager. From there using the arrow keys to select your SSD drive to boot your system. You should now be booting up via your SSD.
At this point you'll need to go to the Startup Disk preferences to then alter the setting so the SSD is your default boot drive.