Replace cylinder head, now no spark.

I just replaced the cylinder head, due to overheating. Everything was replaced exactly how it was, but now the jeep won't start. It seems there's no spark. The coil pack, radiator, thermostat, and all gaskets were replaced and the spark plugs are only a couple months old. Also, the fuel pump seems to be kicking on when I turn the key. Any idea why I can't get it to run? Please help!