The old engines would run as long as the single wire wasn't grounded. These new ones will not run with these wire not connected to anything. I ended up splicing 2 of them together and that leads to a grounding switch. The third wire us yellow and leads to low oil shut down. Any harm in running it this way. It will not run unless those 2 are twisted together. I am not using the factory key switch box. Also I removed the charging coil as I do not need it.