95 pickup engine dies when starter stops

Hi folks

The engine starts fast and I can increase speed as long as I keep the switch in the start position. When I let the switch go to the run position, the engine dies.

I had flushed the cooling systen the day before. I had the upper and lower radiator hoses and both heater hoses disconnected. It started and ran for about 20 seconds on the first try and has not repeated since.

Its a six cyl, Any ideas?

Thanks
Harry

Are you saying you start the engine, then keep the key in START and step on the gas?
That can't be good for the starter.

Are you saying you start the engine, then keep the key in START and step on the gas?
That can't be good for the starter.

I can't disagree with that, but I did it quickly to verify my problem was not fuel. Any ideas on what my problem is?

Thanks
Harry