Ok, so I have this Samsung external hard drive, Samsung s2 portable media 640gb. I have a lot of possible information on it. When I plug it in I can hear it running but it doesn't show up. When I open disk utility I see this
I'd suggest you to try resolving the issue through the command line in Terminal, since you're not left with many options in Disk Utility. Another thing you can attempt is booting in Safe Mode and see if you can access the external from there. Here are a couple of troubleshooting steps from Apple's kb that might be useful to you: https/support.apple.com/en-us/HT203176
You will find the exact commands for repairing the external through Terminal as well.