I think you're right on that one
my front tank stopped working, either the valve went bad or something is clogged. The first tank had a mix of WVO, fresh ATF, some lamp oil, and some UMO, and some diesel and diesel additive. Frankenstein, lol

I also had a pretty heavy leak at injector 1 below the pump. The leak seemed to be coming from the bottom o-ring. I replaced that o-ring with a Viton o-ring, it still leaked a little.
I then added a copper and rubber washer from a lamp and clamped it down. Now, no leak

here's my questions now:

where can I find a schematic of the fuel line routing so I can identify the front tank-to-valve-to-pump and which are the return lines?

where can I get a quality tank valve that is made for WVO/diesel?

thanks