It is essentially impossible to syphon gas out of modern cars. They're designed that way on purpose. That's why modern gas thieves take a battery powered drill and drill a hole in the fuel tank (which can be dangerous for what I hope are obvious reasons). There are other ways to get fuel out of a car but they either involve having the keys and a charged battery (plus making noise and not going very quickly) or tools, even more time, and mechanical knowledge. Plus being vulnerable to being eaten by zombies while you're under the vehicle.