Common Fuel line hose fail? - PeachParts Mercedes-Benz Forum

digieditny · #1 06-02-2011, 11:11 AM

Just noticed a big wet spot below the side of the car (pictured). Upon further investigating, I found that the jack compartment had about 2 inches of diesel fuel in it. There are 2 hoses in there. Are all for fuel? The fuel is coming out of a hole below the car (pictured).

vstech · #2 06-02-2011, 11:27 AM

I think those are vent lines for the fuel tank. attaches to burp tank while filling.
there is also a washer hose back there I think... and possibly drain hose?
oh, and vac lines for the gas flap lock too...

digieditny · #3 06-02-2011, 11:49 AM

Ahh where to start? Is there a section in the manual that explains what each hose does?

Jeremy5848 · #4 06-02-2011, 02:29 PM

Quote:

Originally Posted by digieditny

Ahh where to start? Is there a section in the manual that explains what each hose does?

Unfortunately not. Mercedes assumes that their mechanics have all of the basic knowledge that we owners have to learn the hard way. If you remove the trunk liner on the right side you will be able to see the lines and trace them. There is a drain line for the little filler pipe compartment; if that hose is damaged any spilled fuel or water that gets into the compartment will drain into the trunk. I no longer have a W123 car so I don't remember what other hoses are on that side. There are also little rubber hose jumpers from the fuel tank to the steel lines that run under the car but they shouldn't be able to leak fuel into the trunk.

toomany MBZ · #5 06-02-2011, 02:42 PM

I would think the only way fuel can get to the trunk would be via the overflow hose at the filler cap. Or maybe the seal around the filler pipe.

If the overflow hose is not there anymore, or cracked where it attaches to the car, you'll get diesel in your trunk.

The vent line, located in front of the left rear wheel, sort of, would empty on the ground.

The first pic looks like the end of the overflow hose. Run some weed eater line, or something similar down that hose to check for obstructions.

This pic is of the back side of the fuel filler, on a CD.

charmalu · #6 06-02-2011, 03:49 PM

By TD I assume you have a Wagon, and I see the vacuum tank under the car. the replys you are getting are for the sedans. think the wagon is set up different?

toomany MBZ · #7 06-02-2011, 03:59 PM

The attachments may help.

ashedd · #8 06-02-2011, 04:32 PM

I can go out and look at my TD if you want. There sure are a lot of hoses back there. What exactly are you looking for?

digieditny · #9 06-02-2011, 04:44 PM

That diagram is GREAT! That would help alot. I'll have to investigate tomorrow. I'm pooped. Today, I changed the fuel filters, did vacuum checks, shampooed and vacuumed the interior, and installed air cleaner mounts. Still have to reinstall the noodled driver's seat.

What's weird is that the car has been sitting since last Thursday (may/25). I doubt that it's the drain line. The tank is about 3/4 full.

ashedd · #10 06-02-2011, 06:33 PM

Since it's been sitting.

Maybe the vent is clogged and the pressure differential caused diesel to leak from a questionable hose/connection.

The vent is clogged on my 300D, it leaks something fierce from the delivery valves when there is a big temp swing.

vstech · #11 06-03-2011, 09:13 AM

well like I said, there are no fuel lines in that area, just vent lines, and other system lines.
if the filler vent hose is dislodged or damaged, josling from driving will splash fuel out as it's a pretty large hose. also, filling the car will cause plenty of fuel to splash in the well.
are you sure it's not water in the hole, with some fuel from rust on top? the window above the well is known to have rust issues, and or damaged seal letting water in there pretty easily, not to mention the sunroof drains exit in the vent right above that area (behind the chrome strip) and if rust has gotten it, sunroof will vent right into the well.

mccauleybil · #12 06-03-2011, 10:17 AM

VSTECH: I am still looking for the sunroof drains (right behind the chrome strip) on my 1982 300SD! Any chance you have a descriptive photo to share?

vstech · #13 06-03-2011, 10:44 AM

an SD has the drains in front of the rear tires I believe. I am describing the wagon's drain location in the above post...

digieditny · #14 06-03-2011, 03:46 PM

Ok so I lifted up the trunk liner and found what I believe to be a rat's nest. It was covering up the drain hole. That still doesn't explain the fuel but at least it explains why the fuel was pooling in there.

I believe it's the vent line that's the issue. Is it safe to detach it and inspect it or will fuel spew out? Will fuel spew out of there if it's really hot? We had a couple of really hot days.

pic 1 nest
pic 2 close up of nest

leathermang · #15 06-03-2011, 08:57 PM

Charmalu asked if you have a wagon... Do you have a wagon ?