Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

It can be seen running, begin viewing at 6:45 in your video https://tinyurl.com/2b6ufxw8 .

The way it dies out hints at a fuel feed problem, especially because you have tried another power pack to verify spark.  Remove the needle valve and blow out the tube.  A stray bit of debris may be captured there that blocks the jet orifice.

When it ran and then stopped, at that moment did it seem to have less compression?  If so, check for a tight exhaust or intake valve guide that binds and prevents the valve from closing properly when the head heated.