Wouldn't be surprised if the engine hydrolocked from the fuel in the cylinder, causing the soft threads in the aluminum head to let go. I would go after that problem first, as you might pull the helicoil loose if you do that first and then try to start the engine. Look for open injectors, as IC mentioned, or vacuum lines pulling fuel in. I don't know if the Neon has a vacuum-operated pressure regulator (I don't think it does, I've never heard of any Mopar that does), but I've seen a video of an old Ford EFI van that did this, and it turned out to be the regulator. I kind of doubt an injector. If you've ever seen one fire outside of an engine, you know it's more of a spritz than anything. The fuel pump is capable of moving a lot of fuel pretty quick, but the injector nozzle is so small that not much of it will come out. In the case of a returning-type injection system, in fact, most of the fuel ends up going right back to the tank.