Hi all. Have a 1991 Euro model 250TD that's ... started marking it's territory. I was having fuelling issues after driving 600km (the previous owner advised me to just reset the odometer at every fill up and fill up at 600.) and the fuel gauge was never correct about how much fuel was in the tank. And it was marking it's territory.

I sourced a tank from a petrol W124 estate and had that installed. Fuel gauge works properly now, but I havent even cycled a full tank through the fuel system yet; I normally ride my motorbike to work.

Anyway, I tried to get an idea of what/ where the leak was coming from, crawled under the car and took a peek. It seems to be coming from a T junction looking thing at the forward end of the tank, near the center of the vehivcle towards the right hand side. I circled the offending part (at least I think that's the part.) I can't find it on the parts fiche on this website I've tried using different years and different diesel models to no avail. I'm hoping one of you amazing people can give me some direction.

I can't figure out how to post the picture on here so this link will take you to the reddit site where I was able to post the pic.

Thanks in asdvance for all your help.

couldn't get the pics to work.

If it is leaking near a joint in the pipe or at the connection take brake cleaner and clean everything really well so you can identify the source accurately. There is nothing chronic in that area. Perhaps most likely is a fracture in the fuel line...or a loose fitting?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I noticed the other day when I needed to fill up, that the cap gave an audible "whoosh" when i opened it. "Hmmm. Maybe there's pressure building in the fuel tank/ fuel system." So I didn't fill it up completely; my thought process being that filling it up completely with pressure building in the tank is what created the leak. With more air in the tank (air is compressible), more pressure wouldn't result in a leak, it would just compress the air in the tank.

So, when I stopped, I opened the gas cap, released the pressure, and it hadn't leaked much when I came back hours later.

And, an important caveat; it doesn't seem to leak if I leave it running.

Do those two points clear anything up for anyone?

Have you looked at the overflow outlet inside the gas filler door? There is usually a rubber tube there connecting the overflow with the outlet which drains inside the wheel opening. This hose is a common leak source.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

On my 300d there was some bell shaped thing under the car somewhere in the vicinity a bit forward of the driver's side rear tire that was leaking fuel. It only did it if I would fill the car completely full, and the weird thing is that it would do it a day or 2 after I filled up.

So I found out if I don't fill up to the very top (as soon as I hear the sound of the tank getting towards the top) I stop filling up and that has solved that problem.

Additionally there's a drain hole under the fuel fill up. I think it's there to catch any overflow when you fill the tank. Run a piece of weed eater line down there to clear out any obstructions.

1991 300d 242,800

It isn't coming from that hole, although now that you mention it, I should check the fuel cap itself. It does seem to release pressure when I open it though, so it shoud be sealing tightly.

Mine springs the leak if the tank has a lot of fuel in it and if I don't release the pressure in the tank by opening the fuel cap. To be fair, i've only noticed that twice, and the fuel tank wasn't very full on both occasions.

The car wouldn't start so I had it towed to a mechanic on Tuesday. I replaced the in line filter and primary filter like I always do since changing the tank, but this time it didn't work; the car didn't start.
He'll only get around to it on Thursday as he's fully booked. Which is ok for me as I ride my motorbike to work most days anyway.