I am making an engine toggle switch for a recoil-start engine using two switches wired in series for safety. The engine will shut off only when two "kill" cables on the front have been connected. In the picture below, I have lengthened the wire to make it more noticeable and easier to work with.
Unfortunately, the switches are built to be normally open and cause the engine to shut off when both switches are on (hereinafter called "switch box"). The ideal situation is that the engine status reflects the switch box status: both switches ON activates the engine and turning either switch OFF in the switch box shuts down the engine.
Thankfully I was able to find some answers on how to flip the switches to act normally closed from using concepts from this kill switch post. I also viewed a post about latching relays to potentially use for hooking up to the engine. I spent some time prototyping these ideas and it works exactly as I need it to. Below are the schematic and pictures of the functioning prototype, whenever the LED is ON the engine is OFF because a connection has been established:
For my question, I would have been able to hook up this circuit and been done with it except a recoil-start engine does not utilize an external battery like this prototype circuit and most of the engine kill-switch questions on this forum do. I've noticed through testing that the battery is crucial for making the circuit work. Given that the kill cables from the engine are wired with its spark plug, how would I be able to implement the Normally-Open to Normally-Closed wiring without having a battery? Is there some way to wire the same path the battery creates without using a battery?