Try this, after measuring the thread.

www.newmantools.com/taps/bsp.htm

MOM

good information. Maybe I can dig up the old sending unit.

After reading the info, I'm having doubts that BSP is the thread type.

Whitworth Pipe Threads are used almost exclusively by countries which are otherwise on the metric system.

Japan would be one of those countries, anyone like to add to this?

Should it be BSW [british Standard Whitworth]?

MOM