Various pictures of the path that the hose in hose takes as it makes its way to the fuel tank.

This DIY waste vegetable oil conversion is based around three simple points which are outlined below.

1. At 160° Fahrenheit used vegetable oil will act the same in the injection system as diesel fuel.
2. The Vegetable oil must be filtered at least as well as the stock fuel system filters diesel and the filters should be large and easy to replace.
3. The motor must be shut down and started up on diesel (or biodiesel).

After working with the grease system and talking to other people who had converted it became apparent that looping the fuel return was the only way reliably heat the grease to 160°. If the fuel return is not looped back to the input of the injection pump you will never maintain the required 160° minimum temperature inside the fuel system.

After about 2000 miles, the repair detailed in Part 0 failed.

Another repair was initiated. I went back to Pick N Pull to get another crankshaft pulley and then back to the dealer to get two more crankshaft pins.

This time, I made sure to actually torque the crankshaft pulley bolt to the proper spec - I don't remember offhand what the torque spec is, but I remember it being slightly more than my torque wrench would actually measure. Possibly 120 ft-lbs?

I also used the Red Locktite to hold the bolt in place.

So far, its been driven over 10,000 miles with no problems. The AC compressor was also repaired and hooked up without disastrous results.

A picture is worth 1,000 words!

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 project: Convert the mercedes benz 300D sedan to run on WVO (waste vegetable oil)

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The 6-port Fuel Selector valve has a SPDT switch inside designed for swapping the fuel gauge between tanks. I had ulterior motives however, and wanted to use the switch to light up a two color LED. This is the schematic. Major props to Der Fuhrer for the assist.

The dash with the switches installed. The left switch is a DPDT that controls the 6-port fuel selector valve. The right switch is a lighted SPST that controlls the dump valve.

It was discovered that late model Volkswagens used a type of engine oil cooler that was easy to adapt and use as a heated filter element.

Two of these heated filter assemblies were obtained from the (not quite) local Pick N Pull.

    

This is how the HIH is constructed (from frybrid.com)

Ok, thats the diagram.. lets make this thing in real life:

First, it is necessary to drill the compression to NPT fittings so that the copper pipe can slide through it. Be careful not to damage the compression side of the connector or it will leak.

This is the same basic idea as the diagram, except using real fittings.

Complete Hose in Hose.

After the hose in hose was complete I noticed that the thickness of the hose barb fitting was causing an unfortunate restriction. This might not have been an issue with larger diameter hose (I'm using 3/4" in this application) but I wanted to have as much coolant flow as possible.

So, a 8" long 1/2" thread NPT pipe was obtained. Without barbs, the pipe was much thinner and would allow for maximum performance but perhaps allow the hose to slip off..

.. which is where the file comes in! The hose was "roughened up" with a file which should allow extreme hose pipe grippage

The hose in hose being installed. It sure helps to have a helper at this point.

Routing the hose in hose under the car.

For more check out: Detailed pictures of hose in hose routing

A tank heater was designed using a 60" long gas appliance connector. The connector is inserted into the tank and coiled around the fuel pickup screen. Hot coolant is run though the connector, thus heating the fuel pickup and melting congealed SVO on sub-zero mornings.

Removing the old tank. Installation is the reverse of removal.

Tank after the hole was cut and heater inserted. Notice the vent pipe near the top of the hole! It was only through sheer luck that the vent pipe was not cut with the angle grinder.

Close up of inside the tank. The heater is coiled around the fuel pickup. I think a 72" long connector would have been more ideal as it could have been coiled around the pickup more times, but they are hard to find due to longer uncoated appliance connectors being against building codes. I ordered this one on ebay.

The large hole was sealed using a cork gasket and lots of "gasoline/oil resistant" formagasket. The smaller hole where the ends of the connector protrude the tank was overlaid with metal strips, covered in formagasket, and then covered in JB weld (for rigidity)

The large hole seems to leak ever so slightly, the small one not at all. If I had re-installed the carpeted panel that covers the tank it would have never been noticed.

n the interests of having the best possible running engine to begin with, the following actions will be performed prior to the WVO conversion:

• 1.Change oil, oil filter, air filter, and both fuel filters.
• 2. Removal of EGR system and assorted vacuum lines
• 3.ALDA system service
• 4.Valve Adjustment
• 5. Fuel Hose Replacement
  

The car was purchased for a reduced rate as it was unable to be driven due to a problem with the crankshaft pulley. The engine would start and run, but none of the accessory belts were turning. Luckily for me, Josh had Triple-A and we got it towed to my house for free.

First, major research was done. It seems that crankshaft pulley problems are somewhat common for this type of vehicle. The following links were very helpful. Mad props to the mercedesshop.com forums.

http://www.mercedesshop.com/shopforum/showthread.php?p=115016
http://www.mercedesshop.com/shopforum/showthread.php?threadid=22647
http://www.mercedesshop.com/shopforum/showthread.php?t=141829
http://www.mercedesshop.com/shopforum/showthread.php?t=52125&