[v8volvo]

VW diesels don't like WVO. Biodiesel they love, but WVO is a tricky fuel unless you are doing it just right. Using it straight in the tank with a splash of gasoline blended in is not doing it right. You need lots of filtration and lots of heat, and you don't have either of those things unless there is more to your setup than you described in your post.

Start with ensuring it has a good supply of clean, fresh diesel or high-quality, commercially-produced biodiesel (or a mix of the two). I would run it out of a clean fuel jug under the hood to eliminate an issue in the rest of the fuel system. Install a new fuel filter that is high quality (Mahle, Bosch etc). Fill the filter with clean fuel first. One important thing -- when you remove the old filter, make sure the center rubber O-ring that fits over the threaded part of the filter head that the filter spins onto comes off with the filter! Look up inside the filter head with the filter off -- there should be no old rubber washers stuck up there. Many times the washer gets forgotten in there, or doesn't get put on at all, and that can cause air and fuel leaks or bypassing of the filter media and destruction of the injection pump and injectors.

I suspect your fuel supply is blocked somewhere -- maybe in the tank at the pickup if you have been running cruddy fuel -- or you have an issue with the injection pump or an injector, which might also be caused by WVO. Start by eliminating possible fuel supply issues by isolating the injection system (that is what the external fuel source is about). If it runs great that way, then you need to take apart the fuel system and find where it got plugged. If it still has the problem running off a clean external fuel source, then you need to start troubleshooting the pump and injectors. Is the rear timing belt too tight? If it is, it will wear out the pump shaft bushing, take out the seal, then the pump will suck air when it's running. When it runs, does it run kind of rough? A few months ago I had an injector stick open, which meant it pissed some fuel but mostly let air get forced in through the tip, and then that filled up the whole system with air and it would quit running. You may be looking at something like that too.

Just start eliminating variables and you'll find the issue.

Enjoy the cape! I used to live in Boston. Have fond memories.