Thats bad news if it has been unhooked and ran for awhile...it is the left crank cyl oil injector check valve...it goes down to the oil pump....my right side one was plugged up and i made it a few miles and sized up the cyl...when u hook these up get some of the super small zip ties and put on the hoses...:face-icon-small-sho if you look to the right on your pic u can see the right cyl injector and hose hooked up to it..