Hi John and group,
I have a Vanguard 18 on my 4018 that came from Jims Repair so I am somewhat familiar with the engine. If your Vanguard was used on a 446 as a repower there needs to be some checking into the accessories that are installed on your Vanguard. A stock 446 would have had a Case/Ingersoll tractor mounted regulator/rectifier (R/R) and the Vanguard stator output could have been connected to it which would have left the Vanguard without an engine mounted R/R or a disconnected R/R. If the Case/Ingersoll R/R was not used then the engine mounted R/R would have been used and the 12VDC+ output wire connected to the key switch. The other needed wiring changes are: the Vanguard makes spark by cranking over so it doesn't need 12 VDC+ for ignition, but it needs 12 VDC+ for the fuel shutoff solenoid for the engine to get fuel to run. The kit that I got from Jims had a relay and wire harness that was wired to the key switch to correct the ignition situation.
You need to find the stator output wires (2) and look for an engine mounted R/R.
Get your engine model #, series #, and serial # and got to the Briggs & Stratton web site and download the parts manual for your engine. You can save the parts pdf to your documents on your computer.
Bob MacGregor in CT :thumbsup: