Seeking wisdom of the list!

I am nearing completion of my conversion and have encountered a small
problem .

My injection pump has a device attached to the right lower side where
normally aspirated diesels have a plate fastened by 2 bolts.  The device
appears to possibly be a solenoid valve and has a single pole electrical
connection and a small steel line running to the base of the pump near
the fuel inlet.

My question is what is this device and to what source should I connect
the electrical circuit?

Thanks,
Harry