w115 fuel venting tank? Tell me more

[Topher39]

I have a 1969, 220 gasser - I find two lines coming from the top of the fuel tank, near the edge, and I find a narrow black plastic tank behind my spare tire, and I also find a hard, thin wall plastic pipe that comes our of the front of my cylinder head (broken) that must be tied to this? - now I am not familiar with how this vent system works or what is actually in the plastic tank.

Can anyone shed some light on how the system works and what I need to maintain it? Some of the plastic lines to and from the plastic tank are broken, I know I will have to find some replacement.

Like to loose the gas fumes!

Chris

[Shortsguy1]

Here is a description of the system in a 115.1 vehicle. I know my 220D is a 115.110, but I don't know if this directly applies to your car.

http://mercedes.thatchermathias.com/w123CD2/Program/Engine/615/47-720.pdf

In addition to what you mentioned, there is a small rubber port that hides behind the bumper. This is where the fumes are supposed to vent (again, assuming your gas car is like my diesel).

[Topher39]

That really helps, thank you. I am going to see if I can use some hose from ACE hardware to replace the broken lines. I am not sure though what the line from the front of the engine does . . . I will have to track it down.

[Pooka]

On some German cars from that era a canister of carbon was used to trap fumes. When the car was started the fumes were drawn off and burned in the engine.

This was an air quality thing and not an attempt to increase MPG. Many cars today have these canisters, and some of them collect fumes from the crankcase.

Perhaps this is the reason for the tube coming out of the cylinder head?

[Frank Reiner]

Herewith a diagram of the vent system for a 114, i.e., a gas car:

The vent valve is found under the car at the back of the left rear footwell.

[Topher39]

Thanks Frank! I assume the tube that comes out of the crank is exhaust, not intake . . . I can't feel any suction, nor really a pressure coming out - thoughts?

[Frank Reiner]

The connection to crankcase is used to provide a storage volume for vapors when the engine is not running. When running, the vapors are drawn from the crankcase to the intake manifold via the positive crankcase vent (PCV) system.