Well...depending on what you paid, I'm almost inclined to give you the same advice I gave myself when my newly-purchased used Connie wouldn't start. Suck it up and get it towed and repaired. Now, mind you, for me that came to about $900 on two trips to the dealership, and since then all my work's been done at a private shop or our CEG group. For me, even after dropping the extra coin on service, my car's still cheaper than the other cars I was looking at buying, and I've gotten really attached to it.
So, tell your seller that you won't sue if he agrees (in writing) to cover at least partial costs on whatever repair work the car requires, and go from there.
