JJB, need a little more info.
Are you saying that your tractor will start, but runs rough and shuts off after a few seconds?
Have you made sure it has fuel, bled the lines (two places), checked easily reachable electrical connections to make sure they are tight and generally cussed it out (sometimes that works)?
As for the key, I thought that all the key did was to energize electrical systems (main power & lights). What noise were you expecting with the key turning?