'79 Mercedes Benz 240

[bgkast]

I'm in the process of converting my 240D. I'm using a full return system, HIH for the fuel supply line, with the return line as a HOH on top of that. Also using a racor 225 or similar filter with a heater jacket, 2 6 port valves plumbed as shown in the diagram. To monitor the system I have a veg tank level gauge, oil temp gauge reading temp right before the IP, and a water detector on the racor to let me know if I have a coolant leak.

Let me know what you think.

[JeffNLisa]

A very simple and effective looking system!

Using a 6-port to control which fuel goes thru the lift pump seems an ingenious idea if you need/want to use the same lift pump for both fuels, yet push the fuel thru the filters rather than pull it. As to whether using the same lift pump for both fuels is a good idea, I don't have any experience, so I couldn't comment.

But I do have a little experience with cross-contamination. Depending somewhat on the climate where you live, and a lot on what type of oil you are using, the cross-contamination you will get from a 6-port before the IP will cause you some problems.

These can be as simple as clogged filters, but they will stop you. A MBZ 240 won't have any problem with some VO in the diesel. But a clogged filter will still stop you dead in the road.

Any more, it's just always recommended to use two 3-ports, one for the supply, and the other for the return.

And depending how much heat your system puts in the oil, those Pollack valves may fail over time. I don't see any other heat exchanger in your system other than a HIH for the supply. This will usually give you over 100*F heat in pretty short time, but won't get over 150*F until a long time of driving.

For a 240 MBZ, that may be all the heat you need. And at those temps the Pollack valves may not fail for a long time. Maybe never.

My observation . . .

Jeff

[bgkast]

Thanks for the reply. I was originally planning to use two 3 ports, but several people on a different form suggested I go with the 6 port. I have the valves now so I guess I will try it with them and if it is a problem change to 3 ports. I should have mentioned that I will also be using a Flat plate heat exchanger and a in-tank heating coil similar to the one frybrid includes in their kits. It is regularly below 0 here in the winter so I may also add a 12V heater of some sort. I'll post a picture of my tank a bit later. I just finished it and am quite happy with how it turned out.

[JeffNLisa]

Good.

Will like to see it!!

Originally Posted by bgkast

. . . I was originally planning to use two 3 ports, but several people on a different form suggested I go with the 6 port. . .

Opinions are like armpits, I suppose. Everbody's got 'em, and most of 'em stink!!

But some people have used the 6-port for a *long* time with no issues from cross-contamination.

Also keep us posted about that!!

Jeff

[DieselBurps]

Both of the styles of Pollak valves are largely plastic and may have problems with heat. Your system based on that drawing probably won't have any problems as you probably won't get enough heat without a heat exchanger in place. Either a coolant based one, or an electrical heater should be considered. Definitely put in two gauges and an inline filter in front of the IP - a pressure and a temperature gauge. When the pressure gauge drops from "normal", it's time to change a filter. If the temperature gauge is reading too low (< 150 *F), it's time to be on diesel.

A side note is that all of the fuel you have in between the last 6 port valve's output to the IP, in the IP and on the way back out to the valve's input will be sent to the opposing fuel tank when you make the transition between fuels. This will become a concern if you do a lot of short trip driving and alternate between fuels a lot. It will be worse if you are in a cold climate and the ratio of diesel to WVO in your diesel tank becomes too low. The two best solutions that I can recommend are:
A) Rethink your plumbing and separate the IP output with a valve that is isolated. Time the switchover at idle to figure out how many seconds of delay you need in order to completely purge the lines & IP of the opposing fuel. Get used to flipping one switch to change fuels, and the other after that elapsed time so that the fuel return goes to the appropriate tank.
B) Consider looping your WVO back into the IP. This will increase your purge time, but prevent diesel from entering the WVO tank and overflowing it. You will still get some WVO in your diesel tank though.

After you build and install your WVO system, take a good long look at how well it works. There are always improvements that can be made - evolve it over time! Good luck.

[bgkast]

Good point about the cross contamination. I will try to keep the hoses in this section as short as possible. Anybody have any idea how much fuel is held in the IP? At what tempature do the pollak valves melt down? Thanks for the advice.

[4dantheman]

Interesting design!

Couple of questions.....

Do you plan on purging & if so, how?

How do you keep the VO in the lines heated after you shut down?

[bgkast]

I plan to purge by switching to diesel a few minuets before I shut the car off. Like DieselBurps noted the veg oil or diesel in the lines after the second valve and IP will be returned to the incorrect tank. If this seems to be a problem I will switch the second 6 port valve to two three ports with independent control so I can delay when the return line is switched.

I don't plan to keep the Veg lines heated when the car is shut down. I will start and run the car on diesel until it reaches operating temperature, then switch over to veg oil. I don’t know of any system that heats the lines even when the car is shut off.

[bgkast]

Here is a shot of my tank:

[bgkast]

And one of my coolant tank heater that arrived today.