79 300SD: replacing "skinny banana" rubber fuel hose - PeachParts Mercedes-Benz Forum

#1 12-19-2003, 08:32 AM

There is a hole in the 10" fat black rubber fuel hose (kinda looks like a long, thin, black banana) running between the junction on top of the screw-on primary filter and down to the steel fuel line that runs to the fuel tank. It throbs when the engine is running (I guess that is why it isn't just a hose like a regular one).

After it sprang (and I do mean sprang) a leak, I temporarily taped it up to limp home, and now I am not sure what to call it so I can order a new one. The local MB dealer pondered over diagrams on his computer and told me "You have to order it by the meter --and we don't have it here."

Well, since the hose is clearly not the kind you order "by the meter" --it is fat in the middle (an inch wide) and narrow (1/2") at each end (the ends fit on to the filter housing and fuel line via hose clamps), I didn't order any.

So, when I do order it, what is it called? I told them it was the "fuel hose running between the main fuel filter and the steel fuel line". I *thought* fuel was sucked through the hose from the tank by suction generated from the injector pump... There isn't a picture in the Fast Lane online catalog. Maybe I am wrong, but I don't think regular fuel hose will work.

In fact, the diagrams the dealer parts guy was looking at weren't too clear, and none of the hoses looked like a banana.

Now I plan to order this part online (or call a dealer:-( ), but I gotta know Im getting the right hose!

Thanks, all.

bjcsc · #2 12-19-2003, 08:43 AM

It's called the cigar hose, and if you would have called Phil at Fastlane instead of the dealer it would already be on the way to you house...

#3 12-19-2003, 08:48 AM

Ah, cigar, not banana; yes, come to think of it that IS a better name. I will stick to Fast Lane. Thank you!

reddog · #4 12-19-2003, 09:55 AM

And, it is the return line, not the supply.

#5 12-19-2003, 10:36 AM

and I replaced mine a couple of years ago before I knew there was a difference with regular hose and it has been fine. Notice no difference in the way the car runs and have had vo fuel problems.

lietuviai · #6 12-19-2003, 03:27 PM

I submitted a thread about this very same hose about a week ago and there was a good reply to it.
Injection pump return line hose.

kerry · #7 12-19-2003, 10:27 PM

My 409d has regular fuel line in this location with a fuel filter plumbed into it. Odd, but it seems to work.

#8 12-23-2003, 09:53 AM

Thanks for the feedback.
While I wait for the new cigar hose to arrive (busiest week in the year, of course), I taped up the hose-with-a-hole with "waterproof" black plastic tape that sticks to itself (you wrap it around, overlapping; it is really for temporary fixes for plumbing) after you peel off the backing. It is supposed to stick "tight" after 24 hours.
It worked well enough for me to get home, but the pressure was enough to "bubble" the tape after 3 miles, and fuel was dripping again within 5 miles even though I wrapped the whole 6 feet of tape around the hose!
So there IS no fuel pump! The *injection* pump sucks fuel from the tank, then squirts it back via the return line, right?
Does it still work like this on later diesels, or do they regulate fuel flow differently?
-sg

P.E.Haiges · #9 12-23-2003, 10:44 AM

Sgrist,

That hose has practically no pressure in it unless there is a restriction between the hose and the fuel tank. The flow thru the cigar hose is just the overflow fuel from the Injection pump, the air bleed hole in the secondary fuel filter and the injectors on its way back to the fuel tank. You might connect an air hose to the line and blow it out. Don't forget to remove the fuel cap before you blow out the line.

I suspect the fuel disolved the adhesive on the tape you put on the cigar hose and that's why it leaked.

The engine will run fine with a regular fuel hose in place of the cigar hose. The cigar hose is just to reduce some noise, but I wonder how you could ever hear it over the Diesel clatter. German engineers???? Could you ever see GM or Ford adding an expensive part like that?

P E H

TomJ · #10 12-23-2003, 12:26 PM

Quote:

Originally posted by kerry edwards
My 409d has regular fuel line in this location with a fuel filter plumbed into it. Odd, but it seems to work.

The filter performs the same function as the "expansion chamber" of the cigar hose. Great idea whoever did that. $1 worth of regular fuel hose, $2 filter = same resonant freq modification chamber as the "cigar hose" (but probably does a better job than the cigar!)