I noticed a slight fuel leak on my '76 300D this afternoon. It's quite small so it didn't bother me at first, but then I noticed that there was a hose hanging there as well. On top of the fuel filter there is an apparatus that I think is the shut off , kinda saucer shaped and when it's running the center pops out and when I shut it off it goes back inside the "diaphram" for lack of a better word. I think there is supposed to be some kind of nipple or something that goes on there and this hose is supposed to plug into it, does anyone have a pic. of a 115 chassis engine compartment so I can compare or can someone figure out my inadequate discription of what I'm trying to describe? TIA Tom

Fryer:

Sounds more like the priming pump -- on this model it is up by the fuel filter instead of on the lift pump.

What is missing is the cover. These are sometimes called "palm pumps" becuase you can use your palm on it instead of working a plunger with your thumb.

Check your overflow lines -- if they are bad enough you will get a small fuel leak (you can smell diesel all the time, and a little on the ground). Most of it evaporates off the engine, though, leak may be bigger than you think!.

Also check all the pressure lines -- the clear plastic ones crack with age. You can replace them with standard fuel line after cutting off the clear plastic (brown and very hard by now!) -- the clear stuff isn't available, you have to buy the ends, too ($$$).

If you've changed the fuel filter lately, did you get a new copper seal? They can only be used a couple times before they get too hard and leak.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Now you got me to thinking....I haven't found a priming pump yet. I have looked too! this is attached to the fuel filter and looks like a saucer sitting on top of a square base. You can actually see little sprays of fuel come out of it while it is idling. I'm NOt familiar with the 115 chassis and I don't have any manuals for it so I'm really in the dark here! Remember there is a hose that is the exact right length to connect to this thing. The hose is just laying there right now with a clamp still on it. Hose is about 3/8" I.D. ( excuse me) 10mm I.D. and is connected to a steel line that goes down under the vacuum booster. ( I haven't traced it past this point) all I did was make sure it wasn't a vacuum leak and nothing was running out in copious amounts.

Fryer:

The missing hose is the return line to the tank. All the lines go to the filter housing.

The priming pump is bolted to the filter housing on the fender side. Pressure line to the IP comes off the bottom of the filter housing (this is a canister filter, not a spin-on), return lines come off the rear side of the housing. Needless to say, it is on the suction side.

I'll try to get a photo tonight (I have to make a trip today) -- may take a bit as I'm not digital yet. Priming pump is sorta flat, about 2 1/2" dia.

Return line connects to the filter housing in a sorta three-way connetion -- fuel filter overflow, return from IP, injector overflow lines -- two side connections on a pipe. Return line goes on the end.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I went to ebay and looked into some engine compartment photos and I see what you are talking about. I am missing the "top" of my "palm-pump". I guess there will be an order soon to the Benz-Bin. Also the "homeless" hose that is in the engine comp. isn't the return hose. I have all of the returns hoses in that fancy 3-way all connected. I still haven't traced it to see where it goes. I have been working on VW's all weekend in between my routes. I still have to replace a driveaxle on my .... wifes Jetta before I can get to "my" projects. So, if I understand correctly, I can take an extra VW banjo fitting that I have laying around and put a hose onto it and then remove the bolt on the fender side of the Mercedes I/P and install my "purge hose" and then insert that into the Diesel Purge can along with the 3-way return setup and this should work? (this will keep me from having to mess with those brittle yellow plastic lines that I hate to break) My homemade hose will be where the line comes from the bottom of the filter cannister and goes into the I/P. I will only have to unbolt it from the I/P end. ( of course I will ensure that all the hoses are CLEAN before I put them into the diesel purge can

I would take the suction line from the lift pump or from the primer pump and use it to suck up the Diesel Purge instead. If you take the feed line off the IP you will likely lose prime on the IP (get air in it) that will cause endless trouble. You also need pressure in the IP (provided by the lift pump and the relief valve in the fuel filter and the IP return line) for the IP to work.

I usually just add the diesel treatment to the tank and drive. Much easier, and does much the same thing. Treatments will only dissolve gum and burn off carbon, and pouring it in the tank works the same.

Do you have an abandoned line hanging in there -- leftovers from someone else's replacement work? I don't think there are any other hoses there except the power steering and maybe a cruise control (the early ones were vacuum operated).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!