An '83 Wagon, even non-running, for that price is probably a very Good Deal.
Reasons why an LD28 won't start are limited. Definitely check
the FAQ first, Common Problems section specifically.
Also
ArcataLibra's thread, and
atalamark's thread, where at some point I have covered the hot no-start topics.
To simplify: if it cranks and won't fire, check for voltage above 10v at the No. 1 glow plug during main glow sequence -- you have about seven seconds to check, so hook up your voltmeter
before turning on the key. If no power or very low power, the GP fusible link (right off the battery positive terminal) is a very common failure point (in fact, I bought
this 1983 Sedan a month ago for $50 because the mechanic couldn't start it without ether -- it was a bad GP fusible link connector, and I drove it home without having to use ether!).
If voltage to GPs in that test, use the hand primer pump to check for air in the IP (or clogged filter). Steve wrote up a nice procedure with pictures in
this post.
After that, check for power at the IP Fuel Cut solenoid (arcatalibra's thread shows where) and listen for the "click" of the solenoid when you apply power to it manually.
All good so far? IP Belt is stripped or broken, more than likely. I will probably be changing one this weekend on that $50 '83 Sedan mentioned above, and will be taking pics, but I've covered the basics without pics in the FAQ mentioned above, check it out.