1985 300D SVO pics as I promised. - PeachParts Mercedes-Benz Forum

dieselkid · #1 12-28-2003, 06:06 PM

hope this help you all, I sure know I could have used this when I did this initially.
THanks
just check out :

brittentechs.com/benz

djugurba · #2 12-28-2003, 06:56 PM

Looks great!
First few pictures, I said to myself... that looks like pennsylvania. sure enough!
did you use the greasecar-esque heated filter? What is the purpose of the glass jar? looked almost like a return tank?
my '85 300D will be getting the greasy treatment this spring...
cheers,
Kevin

coachgeo · #3 12-28-2003, 07:05 PM

Thanks for the pics. !!!

Question. How exactly did you deal with the fuel return from the last injector and the IP? It appears you diverted this "after" the junction on top of the fuel filter. Can you label your pictures or draw a map of the system.

What hose is it that you have plugged in the pictures?

dieselkid · #4 12-29-2003, 09:45 AM

The glass jar is a bleeding jar that I bleed the veggie from time to time to remove air bubbles. I used the bleeding jar because I use the fuel return "loop" which is returning the returning fuel back into the injection pump rather than returning it to the tank. The reason for this is that you don't have to run a return line to the veggie tank. It's actually a lot easier, although you''ll have to bleed out the air from time to time which is really simple if you have a setup like mine. If you look at the pictures you will notice that there are two valves after the injection pump. One valve is always open, one is always closed. If one is open and the other closed then the fuel returning is put into the "loop" back into the injection pump. If it is the other way then the fuel is going into the glass jar and that bleeds all the air from the system. Then I just pour the contents of the jar back in my veggie tank. Very simple actually.
The veggie filter with the copper coolant coiled around it is homemade and very easy to make. Just buy some soft copper and make your own. I used a 1981 diesel rabbit filter housing for the system. It is actually 3 times bigger than the stock mercedes 300d fuel filter housing. Changing filters takes about ten minutes and costs about 7 dollars to get a new one. It works great though.
Hope this help out.

coachgeo · #5 12-29-2003, 10:33 AM

ahhhhhhhhh a bleeding jar. So you are returning hot diesel back into the IP also and not using a solinoid to return it to the tank? BTW some speculate this hot diesel could dammage the IP in the "LONG" term.

To avoid the need for a bleeding jar for the WVO fuel return loop you may want to consider what is coined as a "Modified fuel return loop" Ths method came out of input found here.

In general it works by feeding the fuel return loop thru a common 3 port gasser inline fuel filter. You place it before the loop "T's into the IP's incomming fuel hose. These filters have a built in "3rd" port (bleed port) that you feed back to the tank thru the normal return system. They cost 3 bucks or so. Do a search on "Modified Fuel Return Loop" at the linked site above for more details.

dieselkid · #6 12-29-2003, 05:24 PM

Not sure what you mean by hot diesel. The diesel fuel that I use in my car never gets hot. The SVO that I heat up is hot, but it won't damage the IP otherwise SVO would be inconceivable and we wouldn't be having this conversation, we would be talking about biodiesel.
We'll get it worked out:p

coachgeo · #7 12-29-2003, 05:48 PM

Do you have a full time return loop; as in rather on diesel or WVO will the fuel go back to the IP vial the fuel return loop? If not that, do you have a solinoid valve that you switch when running on diesel that sends the diesel return back to the diesel tank?

If you do not have a valve to send diesel return back to the diesel tank then you will be sending hot diesel fuel out of the IP back into the IP via the fuel return loop. Hot diesel is suspected to not burn as well and also cause long term damage to the IP.

Also, are you aware that the junction on top of the fuel filter housing on this car is where any air that made its way into the screw on fuel filter and any air out of the returns are sent back to the fuel tank? All this air is sent back to the tank via the fuel return system. Because of this on the 300D when the fuel return loop is active; as you have it plumbed, you will also be sending any air that that made its way to the main fuel filter into the IP. Not a disaster but this is why you have to bleed the system occasionaly (or use the modified fuel return loop as I described earlier to bleed it for you)

dieselkid · #8 12-29-2003, 11:45 PM

The diesel that I burn in my car never gets hot. I'm still not sure what you are talking about here. As far as the banjo bolt being welded off, that is necessary if you want this system to not mix diesel with Svo or vise versus. THe air is really not a problem because it builds up in one part of my clear fuel line and when I bleed the system it takes care of that problem. The bleeding might take like 10 seconds or something. THe nuisance isn't even worth the time we spend talking about it. Anyways if you were standing in front of my car I could explain all this a lot better. I'm really curious though what you are talking about with the HOT diesel thing.

coachgeo · #9 12-30-2003, 12:23 AM

ahhhhhh.... welded off banjo bolt. Your right.. its hard to tell just from pics LOL. Man do we definately need a description of of both diesel and WVO fuel flow path in your set up.

As to hot diesel: Anything that goes thru the injection pump (IP)comes out the IP return line at about 120+ degrees once engine is up to operating temprature. So if your fuel return loop is full time operation thennn when you are driving on diesel you have hot diesel going thru the return loop and on back into the injection pump. This is why I asked if you had a valve to send diesel return out of the IP to the tank or not?

In normal operation the diesel is part of what cools the injection pump and keeps it efficient. If you have a full time return fuel loop then the hot diesel is not cooling the IP anymore and it can prematurely wear out the IP; Sooooo it is therozed.

With WVO it is good to have the fuel return loop cause the hot WVO exiting the IP helps the process of thinning the WVO out. That is why they do the fuel return loop in the first place. WVO also still cools the IP even though it is hot. Complicated to explain why but it is theorized that it does.

Dont you love this exact science :p

dieselkid · #10 12-30-2003, 11:28 AM

The diesel that is supposed to be returning to the diesel tank when running at normal operating temperatures is returning at a minute amount. If you drive five miles at normal operating temperatures then you probably filled up a 20z soda bottle with diesel. When you compare that with the cold diesel that is entering the Ip and then mix hot with cold you really don't have any kind of problem. Don't forget that the fuel return loop is mixing with the cold diesel that is entering the IP. As far at the returning diesel being 120 degrees at operating temperature. That really just isn't the case. I've bleed the returning diesel after I drove 4 hours at 75 miles an hour and the diesel was luke warm. Anyways it sounds like our conversation is making more sense so I'm happy.

coachgeo · #11 12-30-2003, 07:56 PM

Quote:

Originally posted by dieselkid
I've bleed the returning diesel after I drove 4 hours at 75 miles an hour and the diesel was luke warm. Anyways it sounds like our conversation is making more sense so I'm happy.

Thanks for that info. I used a infrared thermometer and measured the temps of the filter housing next to the banjo bolt 9 times over a 1350 mile trip. Avg. temp was F136.22...
This was with normal fuel return (no loop) using a blend of WVO/Diesel, in the summer from OH to FL. Engine was same as yours but vehicle it was installed in was much slower and heavier. AKA... engine was working harder. (installed in a Unimog)