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[ToddT]

I've run with the two pumps/check valve scenario for a few years. It works pretty well. However, twice now I've had check valves fail. Right now my FASS pump is out of the system (shorted out) and it is clear that the diesel is back feeding through the check valve on the WVO side.

I'm leaning toward going back to using a three port solenoid valve to switch between the fuel supplies.

On the diesel side, I'm using a Mallory fuel pressure regulator. This way, the excess fuel goes back to the tank. I like this idea in that it keeps the fuel circulating and being polished as it goes through the filter over and over. Each pass through the filter cleans it up a bit more.

The FASS doesn't call for a regulator and therefore is pushing against a lot of head pressure, in my opinion. That means heat. I'm wondering if that is what caused mine to fail. These pumps put out a lot more flow than our engines require. I fear the heated oil will cool as it goes from the tank (FPHE, Hotfox, etc in the back) all the way to the engine.

Therefore, I'm leaning toward adding another FPR at the engine for the WVO side. It will divert the bulk of the flow back to the veggie tank. That means less time for the oil to cool as it travels from the tank to the engine. And again, more passes through the filter... and that means cleaner oil.

Someday I'll go to the regulated return... when I get the courage to dismantle most of the stuff off the engine so I can actually get to the fuel ports on the back! In the meantime, this two pump system works well. I don't turn mine on and off. The diesel pump runs all the time. This way you have a full-time fuel system running all the time. If the grease side should fail for whatever reason, it won't even cause a blip in operating.