1994 international 9400 stall

Hello I'm new to the hauling industry, I've recently bought a 1994 international 9400. I was told it has a Cummings 350. The other day while shifting it stalled. The truck will start but for only a few seconds before shutting down. The headlights will work after stall so there is still juice in the batteries, but when the key is turned over ignition shorts out. if you turn the key fast to start it, it will crank. The only time it stayed on was when the accelerator was held down. Any ideas on what may be the cause of this? Any information will help. Thank you.

 

Thank you all for your help. The solution to this was changing the ignition switch and fuse for ignition.