I have attempted to convert my 1995 T444E to run on WVO but I am having issues.
This is my current design, except I replaced the check valve (Purple circle) between the WVO filter and the WVO pump with a 12V shut off valve.
From what I first thought there shouldn't be a path for diesel to get to the engine in WVO mode but I think I was wrong, because when I took the bus for a test drive I burned diesel in WVO mode at a normal rate while slowly backfilling the WVO tank.
I took another look at the drawing and found I did initially overlook a spot on the stock filter tower. The fuel pressure regulating valve is mounted to the stock fuel filter tower and maintains correct pressure in the injection rails. It has an internal passage though, that goes directly into the filter tower to the dirty side of the filter. Here is a fuel flow diagram showing it.
And here it is on the tower.
I know, obvious thing to totally overlook, and I even replaced the stock fuel filter so I had to look right at it, but I did. So my thought is that this passage is under low pressure from the stock transfer pump. From here unfiltered diesel was pushed out of the filter canister and down the return line to the suction side of the WVO pump, which then sent it to the injection rails to be burned.
So my question for the skoolie community is, is this internal passage an integral part of the fuel return system? Or, is it there just to shortcut having to pull unfiltered diesel from the tank. And with that, could I plug the internal passage without affecting the return valve or does it require a certain backpressure in that passage? Because if I can plug that passage than I think it might work.
Also, if anyone has any other schematics or drawings of the T444E fuel system they could share I would be forever grateful.
Edit: Not sure why the pictures aren't working, but I've added links, and my WVO system schematic is on my other "Junebus" build thread