Fuel return modifications - PeachParts Mercedes-Benz Forum

coachgeo · #1 08-11-2003, 02:27 AM

Thanks folk for all the help thus far in my dig for information to help me better design my WVO conversion on my dieselized Mog.

OK another question, hope ya dont mind.

I see now there are TWO returns to the fuel filter on the 617. One is from the IP and the other from the injectors. Both of these or fed into the banjo bolt atop of the Fuel Filter. The banjo itself act like a T with bleed from the filter below.

Goal: To put these two returns into a selectable valve to where I can select between having the return system act normal (when Im driving on diesel) or to work for WVO (return(s) "T"ed into incomming fuel lline just before the fuel filter.)

Problem is I have a selectable valve that only allows for two flow paths. but I have 3 flow paths Im dealing with. Two returns; both into banjo, and the new return "T"ed to incomming fuel line for WVO use.

Logic says just "T" the two fuel returns together prior to the valve and whala.... problem solved. Now the valve allows two flow paths. Flow one would be for DIESEL USE where both returns flow thru the valve then out to the banjo. Flow 2 (WVO USE) would be warm return fuel from both return lines flow thru the valve and on to a "T" in the fuel line comeing into the fuel filter. This "T"ing of the fuel returns prior to the valve is my plan.

Question is the setup after the Valve for diesel use. This side has been "T"ed together before the valve .... so now.... should I use a "T" after the valve to split things again and go to both of the orginal return ports on the banjo.... or just keep it one line and block off one of the banjo ports. The Banjo essentially was "T"ing togehter the two lines anyway.

another simular option for the DIESEL SIDE is come out of the valve into a regular prefilter then "T" out of this into the two banjo ports. Not sure if this is an advantage at all or not.

coachgeo · #2 08-11-2003, 07:24 PM

did I totaly baffle y'all on this one heheeh..

Hope not. Ask me questions to clarify anything you might not understand up above.

This info is Super important for the last part of my conversion. Being able to switch between the two fuel return paths (to top of fuel filter or to the incomming fuel line) will help so much when driving on diesel and not the WVO.

I dont want to send hot diesel thru the IP its not good for it from what I understand. Hot WVO is fine...... that's a long explanation why.

Again..... thanks for ANY info someone can provide and PLEASE ask me questions to clarify my jibberish so you might be able to answer my questions.

BoostnBenz · #3 08-12-2003, 11:01 AM

I recall reading several places that heated diesel doesn't really matter, then again they don't really know our specific IPs either. (I read someone's theory that the reason fuel is returned to the fuel tank is to keep it warm for winter driving.) I also read on some of the WVO sites that it really doesn't matter if the WVO heads back to the diesel tank because it is such a little quantity. I would prefer in my own setup if I could get a 6 port valve and have it just sent back to the WVO tank. It just seems to me that any WVO in the diesel will raise the cloud point a little bit. I'm not following you coachgeo, I've never really looked at our fuel return system before, can you build up a simple diagram?

coachgeo · #4 08-12-2003, 11:05 AM

Im not conserned with sending diesel to the wvo tank or visa versa.

I 'm just wanting to protect the engine and not be driving on hot diesel. If enough folk agree that hot diesel wont matter then I can forgo this valve. Certainly would make me happy.

coachgeo · #5 08-12-2003, 11:40 AM

Large circle is the TOP of the fuel filter.

Small cirlce is the TOP of the Banjo

This is one way of doing it. The two returns "T"ed together feed into a valve. If diesel is selected (A) then the diesel runs straight out of the valve to one of the banjo ports. The other banjo port gets blocked off

coachgeo · #6 08-12-2003, 11:48 AM

http://bbs.mogstink.com/album_see.php?id=49

this one uses a "T" after the valve to split the diesel apart into two lines again and feeds the fuel into both the banjo bolt ports as it is normaly set up.

BoostnBenz · #7 08-13-2003, 10:58 PM

I'm starting to think of the biodiesel route again. It'll probably cost the same upfront, but I can use it year round (if I recover the extra methanol it should only cost ~$.40/gal). I seen a good setup with a used water heater as the tank. Use a pump to stir, and a vacuum pump to suck it in and help recover the methanol into a paint pot. There were some more elaborate ones out there which had a container to hold all the glycerin, another for the biodiesel....

coachgeo · #8 08-14-2003, 03:27 AM

Quote:

Originally posted by BoostnBenz
I'm starting to think of the biodiesel route again. It'll probably cost the same upfront, but I can use it year round (if I recover the extra methanol it should only cost ~$.40/gal). I seen a good setup with a used water heater as the tank. Use a pump to stir, and a vacuum pump to suck it in and help recover the methanol into a paint pot. There were some more elaborate ones out there which had a container to hold all the glycerin, another for the biodiesel....

Once you factor in labor involved in every ounce of BioD produced compared to the Labor of converting your car ONCE and the filtering labor you find WVO is far cheaper.

Cold weather.. Dana runs full time WVO in upper Michigan. Others are further north in Canada.

BoostnBenz · #9 08-14-2003, 10:39 AM

What I suppose is slowing me down is that my drive is something like 30miles each way, so the first few minutes and last few equate to around 20% of the trip. So that means I'll probably end up making bio for that portion, but if I already have to make some.... Another thing is if I get a WVO tank I'd want it to hold about 20gallons which I believe would make it 10" deep, then 20gallons of it weighs approx 180#, which could be enough to make the springs start sagging (or in my 84's case, there would be no more spring). Finally I'm not keen on drilling holes in my trunk and running new coolant lines the length of the car. How do you know when your WVO tank is getting empty? Surely you can't wait to start sucking air as then you could be SOL, do you just have to keep looking in it or is there a way to get a gauge sent up to your dash? (I was wondering if there were a switch that could be wired up to a sender to have little LEDs to light up the amount in it.) Do you guys boil the water out?

With all of that said, I finally bought some filters from McMaster Carr, I got 7 for $23.

I bought one real expensive one and six decent ones, the decent ones filter to 1 micron, but the expensive one is supposed to last 3X longer but filters in the 1-5micron range. Eventually I should end up doing SOMETHING with some WVO.

coachgeo · #10 08-14-2003, 11:49 AM

ok..... back to more specifics please about the 617 fuel filter's return lines. This is my only area of question; Wondering about what is the best way to plumb the two returns into a valve, and what is the best way to plumb the OUT of the valve back to the Fuel filter. The valve is intended to select between the normal fuel return path and a WVO fuel return loop.

BoostnBenz · #11 08-14-2003, 01:22 PM

Quote:

I can also gauge the amount of oil in the tank by judgeing the temperature dif in the AM because the oil will maintain it's temp better than the drum will.

I'm not following you here, are you saying judging it by the amount of time it takes to heat up in the morning?

Actually doesn't the diesel cut the WVO if it starts clogging up on the filters, versus biodiesel really wouldn't would it?

The hardest thing about implenting that idea would be the valving. You'd have to have diesel going in and return to the WVO tank.

I would just say to cap it off, what gain would it give you? There should be enough flow for the valve to allow fuel back into just the IP's return. I don't see any reason why you would want or need to use the injector return line the way you have it hooked up.

BoostnBenz · #12 08-14-2003, 01:48 PM

I edited my previous post to answer. However, I wonder why you just don't run a new fuel line up from the tank to the motor and get a 6 port valve after the cigar hose. Hook up the one return back to the tank, then the WVO return would just T back into the WVO feed before the valve. Then you'd only have one switch to throw, and the cigar hose could be used to dampen any surges which it supposedly does (you would be cutting this out on WVO mode in your current setup).

Ok that makes sense now Mespe, thanks.

BoostnBenz · #13 08-14-2003, 02:14 PM

Here is an idea for you mespe, while in long periods of time it may not work as well but would cost less. If you were to utilize the auxiliary pump which we already have to circulate the coolant after the car had been setting, also insulate the WVO tank a little bit, that would buy you some more time.

Heh, you posted the same time I did. Yes that does make sense.

coachgeo · #14 08-14-2003, 02:23 PM

Excellent info guys.....

now once again steering back to the orginal intent of this thread.

Suggestions about the ACTUAL plumbing of the return lines, specifically the area after the selector valve and to the fuel filter banjo bolt.

BoostnBenz · #15 08-15-2003, 07:47 PM

I believe that the W123, W124, and W126 (probably all MBs) have a pump in the lower right front which pumps the coolant through the motor into the heater core while the motor is off. So if you're tapped into that same side of the thermostat then you'd be able to give your WVO tank a little more heat from this.

What sort of suggestions are you angling for? Your model 1 appears right on to me. You'll just have a hose whatever size OD your fittings it Ting into the current 7mm feed fuel hose for your WVO's return. The diesel return is automatically correct because of your setup.