You are going to ruin something if you haven't already. There is a passlock/security sensor in the lock cylinder housing. If you removed the ignition switch from the housing it is really tough to get everything back together properly again. I have been doing it for15 years and still have trouble sometimes. There is a magnet on the lock cylinder that passes by the sensor on the housing. The sensor sends a code to pcm to allow fuel. That is why it starts and dies. The ignition must be rotated for it to start and stay running. Gm dealer can supply a new housing and cylinder coded to your vin/key. Will need a relearn procedure after installed though.

Rut roh...