If (Why do you bring up sticking rings????) you suspect a problem.

Tie off (Down) the Emergency Stop Lever and using a ratchet crank the engine
around 4 revolutions to see if anything Binds.

Did you take any Prophylactic measures with the Diesel in the Tank?
(Adding 16 oz. "Pri-D" and 8 oz."Startron" to the Tank before filling.)

I'd change the engine Oil to a Fully Synthetic ('Purple,Red Line,Delvac)
With a new filter.
and Feed the Primary Filter from a 1/2 Gallon container of New Fresh Diesel.
Glow that baby and fire her off.

OR follow Layback's instructions.

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'84 300SD sold
124.128