PeachParts Mercedes-Benz Forum - Help..still fumes in cabin on 190E 2.3-16V

I have posted on here before, and this problem still exists..no matter how many times I feel I have solved the issue.

We have replaced the external vent valve, although the original did not appear clogged. Have replaced the regeneration valve (engine compartment) most hoses coming from or to the carbon cannister, the carbon cannister itself, the fuel hose coming from the tank to the pump (flaired fitting was leaking).

It now appears that fuel continues to leak from the gas cap...and run down the fill pipe, past the rubber mounting grommet..instead of out the drain hose...will replace the rubber grommet soon. However this does not explain why I am pushing fuel out the gas cap.

I assume that there is a safety vent mechanism in the gas cap which will vent when pressure in the tank get's excessive...I am aware of the purge/regeneration valves, and the vent valve outside the tank, but assume that as a safety precaution, the gas cap remains vented, in case the std. vent system get's plugged. I have tried at least 5 different fuel caps...with no improvement.

I can only assume that somehow I have over pressure in the tank on an intermittent basis, which periodically pushes fumes and fuel out of the gas cap which then runs down the outside of the fill tube (and consequently through the trunk of the car). Given that I have replaced the various items that could cause restriction in the vent system, I am stumped. I have even run the car with an elbow where the vent/regeneration valve is located. This reduced the incidence of fumes, but they still existed slightly first thing in the am. Am not sure other than making sure that the fuel pump has positive flow most of the time, why a two way vent valve is necessary in the vent line...car runs ok with just the elbow.

Fumes are currently bad first thing in the am before start up, and when driving with the window cracked, indicating that they are coming into the cabin through the rear vents..consistent with the cap fuel leakage However there will be no fumes for the first 10 - 30 minutes of driving (other than what exists in the cabin at start up)...again indicating that the leakage may be pressure related.

We have had various leaks in the system show up, and repaired all...there is no longer any visual leakage showing up, other than what seems to be coming out at the gas cap. Engine compartment has never had any visual leakage, nor any odor in that area.

Fuel tank has been removed, and pressure tested, and smoke tested as well, showing no leaks. I have an alternate fuel tank which could be used to replace existing tank. We have put a flat plate across the fuel fill mouth with bluing, and it appears perfectly flat.

Stumped....have had the car on a lift at least 15 times or more to try to resolve this..driving us all crazy.....Help...

A couple of other questions...first..and I cannot remember seeing it...is there a rubber section of hose above the vent valve somewhere? I once had the inner rubber lining on a fuel hose come apart and work like a check valve.(different make and model of car). Second..is there an internal screen on the vent line in the tank?