I recently bought a '94 Chevy Lumina van from a HIGHLY reputable dealer. It pulled to the left terribly, and it was a hard and steady pull. Turns out the vehicle had a bent control arm and spindle from collision damage. The dealer promply refunded all my money once I figured this out. In a collision, the frame can easily be bent, rendering the car useless for alignment. You may have just a bent control arm or spindle, or the frame holding both could be bent, making it much harder to correct (You'd have to straighten the frame). Go over the car carefully to make sure you don't see any signs of collision repair (paint overspray, very new looking paint, or just sloppy workmanship on body panels).