You cannot compress a liquid. If you dumped so much fuel into the engine that it filled the the area of the combustion chamber, it would lock up the engine and probably bend rods or break something. The engine will be wrecked. That is why I asked if you tried turning it over without the sparkplugs. Without the plugs, the fuel would be forced out of the sparkplug hole and the engine would turn over. Then you could do a compression check to start checking for damages.