Sounds like the wvo may have polymerized inside the IP, and that has gummed up the works.

Disconnect the injector hard lines at the IP.
You should get decent fuel flow out of the delivery valves when cranking the engine.
If not, disconnect the glow plug relay and run ATF through the IP.

Let the ATF soak in overnight and repeat with fresh daily ATF soaks in the hopes that you can eventually clear out the gunk.
Might take a week or more to see any positive results.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022