I've got little to add to the advice above, but based on your post count, I'll point out a reference to the unique shape of the TD's tank that might affect fuel supply: How does the tank screen work on a 123 wagon

I'd start with the basics and remove unknowns. ah-kays advice about a separate clean bottle of fuel is good, since that can isolate tank problems from engine problems; as is ensuring you've got a good boost pump.

I think I've read where the black Bosch pumps weren't recommended for WVO, so your PO may have kept the old "poker chip" pump for his WVO use (so-called becase of the thin white disk with ridged edges) and that could be leaky.