The project: Convert the mercedes benz 300D sedan to run on WVO (waste vegetable oil)
Stage 5: The fuel system.
A picture is worth 1,000 words, right?
One thing the picture might not make clear is there are a total of two fuel valves installed. One 6-port and one 3-port. This drawing is
a schematic, and has nothing to do with the physical placement of the components involved. An astute reader will realize that the two 6-port icons are of course the same physical valve, and the injector return and IP return lines meet up with the cigar hose with three port banjo bolt on top of the diesel fuel filter.
The fuel system design accomplishes the following:
- 1. A looped return to increase WVO temperature.
- 2. Allows for easy and fast purging of the fuel system. This also speeds shutdown time by having the ability to "dump" diesel fuel through the system and into the veggie tank.
- 2a. This does have the side effect of decreasing the vehicles ability to run on diesel fuel. Diesel fuel is not designed to be heated, and loses its lubrication properties at high temperatures. In fact, the whole reason for a fuel tank return on a diesel is to give the fuel a chance to cool in the tank before being recirculated. This is not a problem for bio-diesel however.
- 3. The filter elements for both fuel systems are completely independent. If one becomes clogged, the car will still run on the other.
In the future, an electric pump for the WVO system may be installed. This would free up one set of ports on the 6-port fuel selector valve, which could then be used for all sorts of mischief such as recirculating the veggie system while driving on diesel or setting up a system to pump diesel backwards through the veggie system.
This is what the system look like in reality:
As you can see, the windshield washer tank was sacrificed in order to install a 2gal (bio)diesel tank for startup and shutdown. The massive air cleaner assembly was also removed and a K&N style filter was installed.