Best start by saying that I've never owned a diesel, but I did work on them in the USN long ago. Here's my interpretation:
Parts # 6 are starting aids, which to me says they're 'choke' injectors. They're akin to the choke on an old carbed gas engine, used to give a richer mixture when starting. Part # 2 is a solenoid (operated) valve, probably energized on cold start and allowing fuel to flow to #6.
At a total guess, it's a generic solenoid valve, with several uses. The second terminal may be to allow for a ground wire when needed. Yours may not need a ground wire, since it may ground thru the mount or the metal line to the 'start aids'.
Check for continuity & resistance with a volt-ohm meter, measuring from the wired terminal to both the body of the solenoid & to unwired terminal. If I'm right, there'll be almost no resistance between the unwired terminal & the body, but there will be measurable resistance between the body & the wired terminal.
Good luck, both with it, and with following my gibberish... ;)
Jim, "The old expert, often wrong but never in doubt."
