Hello avaition people and pilots.
Isn’t there a valve to isolate a faulty engine from flowing air into the cabin space?
Yes, there is. Plus 2 different fuel shut off valves and hydraulic shut off valves.
This is right from Boeing.
“Pulling the fire handle arms the fire-extinguishing system and shuts down the engine. It also shuts down the fuel furnished to that engine, the pneumatic system, the hydraulic system, and the electrical system associated with that engine.” Also, There are also 2 halon fire extinguisher bottles located in the wheel well area that can be be used to fight fire in either engine. Fires need 3 things to start. Fuel, oxygen and some sort of Ignition source.