Model A turns over, but won't start

[jjspock]

I am trying to sell a 1931 Model A coupe for a friend. It's sitting in my garage and started easily when we put it there 2 months ago. I've been starting it regularly and last time I did, I forgot to shut off the key. Now it turns over but as soon as it fires up, it stops firing, the starter disengages and I can hear it whirling. I put in a new bendix and a new coil but no change. It has spark and gas. Can you help? I'm flummoxed.