MB fuel lines in engine 606 - PeachParts Mercedes-Benz Forum

onagrote · #1 04-28-2008, 09:13 AM

Hi guys!

I'm new here but have found valuable information by reading through some of the posts here. There is a lot of expertise here! ;-)

I had a question about the fuel system in my 1996 E300D with engine 606.912 and was looking to get some help.

In the image attached, I am trying to figure out if line 90/x goes back into the fuel filter or is just attached to the housing of it. Maybe once I take it apart I could answer my own question but I am just trying to figure out where things go to without taking anything apart.

(1) So, I think 90/x merges with 90/3 into 90/5 which returns to the tank. I think these lines are only mounted to the housing of the fuel filter. Am I correct here?

(2) And also, is diesel always flowing through 90/x?

(3) And last question. If I start replacing some of these lines, how can I purge them to make sure there is no air in them after I put it back together? Or will the car do that automatically?

Thanks in advance for your help!

Chris W. · #2 04-28-2008, 01:01 PM

I can't help you with 1 and 2, other than to say that if you want to replace these lines, just pull the intake manifold and get busy....

Regarding No. 3, no purging is needed. You're just going to have to crank a while until it starts again. If you happen to have pulled the main fuel filter while doing the lines, fill the new one with diesel and then reinstall it.

Best have a fully charged battery, and give the starter a rest now and then to let it cool off.

Rgds,
Chris W.
'95 E300D

onagrote · #3 04-29-2008, 05:37 PM

Anybody else wants to give it a try? ;-)

[bump]

TMAllison · #4 04-29-2008, 05:58 PM

#1 & 2 are correct.

When running, fuel is flowing through all of the lines all of the time. When shut down, line 90/2 will drain back towards fuel thermo an inch or two. Will immed refill upon start up.

drgreenthumb · #5 04-29-2008, 08:29 PM

Quote:

Originally Posted by onagrote

(1) So, I think 90/x merges with 90/3 into 90/5 which returns to the tank. I think these lines are only mounted to the housing of the fuel filter. Am I correct here?

90/5 is a black line, 90/3 is the braided return line from the injectors, and 90/X is a clear line. 90/X connects to the fuel filter housing and the other two lines connect to 90/X. 90/3 connects to barb and 90/5 uses a clamp to connect.

90/X actually connects to the side closer to the head. If you change that line you will need a small green o-ring to go on the overflow valve.

I just changed all the plastic lines on my 606.91. It's not that hard with the intake removed.

onagrote · #6 04-30-2008, 08:48 AM

Thanks for the explanation guys! I was trying to understand the fuel flow in this engine so I can figure out the best place to cut into it to add a WVO flow from a second tank without getting any of it back into the diesel lines or leaving any of it in the IP or nozzels.

This might not be the right forum but, do you guys think bringing the hot WVO into the IP at 70/6 (green) and then collecting it again at 90/5 (cyan) would completely isolate the diesel flow from the WVO flow (except for the IP and nozzels, of course)? Before turning the car off I would have diesel back in the IP and nozzels and have switched to the diesel flow so the WVO would be completely blocked off.

I've heard how complex these w210 engines are to convert to WVO so I am afraid my idea above has some flaws I am not seeing.

Any advice is greatly appreciated. ;-)

TMAllison · #7 04-30-2008, 12:31 PM

See post 64. http://www.peachparts.com/shopforum/showthread.php?t=119974

Get a heater too.

notfarnow · #8 04-30-2008, 12:47 PM

I had to fiddle with my fuel pumbing a bit, it's working great now set up like this:

http://jakesbenzconversion.blogspot.com/search?updated-max=2008-04-22T23%3A15%3A00-07%3A00&max-results=1

You have to plug the port on the filter housing where the IP return line meets the return fuel from the injectors. Otherwise, you'll get veggie leaking into your diesel.

onagrote · #9 05-01-2008, 08:33 AM

Thanks Jake! I actually came across your website yesterday and really made my day! ;-)

I was going to post a correction here to my #1 assumption since you have discovered that my assumption was wrong (a small percentage of the fuel in 90/x and 90/3 go back into the fuel filter, they are not just mounted on the housing), but you are kind of showing that in your diagram above so it should be clear enough now.

Thanks again for sharing! And you've made a very neat convertion! Something to be proud of. ;-)

Take care...

notfarnow · #10 05-01-2008, 10:02 AM

Thanks!

FWIW, conventional wisdom is that the intake manifold needs to come off to get at these. I had mine off when I converted mine, and took advantage of the opportunity to change my GPs.

Anyway, I later found that you get pretty good access by removing the fuel filter housing & windshield washer bottle.... even with the intake manifold on. I had an air leak I had to chase down, and was able to remove all the lines without removing the intake manifold. It's a bit more awkward, but not impossible.

Just the same, it's worth taking the IM off to do your GPs. I'm doing mine (removing, reaming, anti-seize and reinstall) every year from now on.

onagrote · #11 05-05-2008, 12:05 PM

Jake,

One last question.

If I plug the port on the filter housing where the IP return line meets the return fuel from the injectors, and add my own separate fuel pump for the veg oil, would my flow hookup in post 5 work? I am trying to see if I don't re-plumb the IP/pump as you did and leave them alone, and add the veg oil system completely separate so when I switch to diesel it flows the same way as when it came from factory.

Let me know what you think, otherwise I'll do it your way. ;-)

Thanks again!

Cesar

notfarnow · #12 05-05-2008, 01:49 PM

Jeeze I'd really have to sit down and figure that one out... the thing is understanding how that would work when the ESV is shutting the engine down... it actually reverses the fuel flow into the IP. If you bung that flow up, you throw a check engine light.

I don't know of ANY e300d conversion that uses a seperate fuel pump for veggie.

In fact, I had originally purchased a Holley Blue pump w/bypass valve to use for my conversion, but I wasn't able to find any fuel flow setups that would work.

onagrote · #13 05-06-2008, 12:59 PM

Thanks! I think I'll stick to what it works... ;-)

Take care!