If I fill the fueltank completly full, the engine behaves erraticly and nearly dies. If I drive it for a while it normally gets better. I changed the bleeder valve (944 605 240 01)hoping it would solve the problem, but no change. Afther driving the car for 60 km (I stopped at 30km to open the fuel tank cap, but that did not improve things) I parked in my garage and it immediatly started to vent fuel from under the rear part of the left door (charcoal cannister flushing air pipe p.126?). I estimate 0,5 liter before it stopped. When I open the fuel tank cap I normally hear a hiss, as air enters the tank. If I just fill apx 40 liters of fuel( afther fuel wrn. light) everything works ok. Does anybody have any suggestions?
Mortex 90 C4

 

As far as I know there is a evaporaton container which collects the tank fuems, so that they cannot come in the inviroment. Sometimes the tank [which contains carbon that absorbs] is full and can't take more fuel fuemes.
If that happens then the engine get's too much of both, fuel thru a normal way and the high % fuems. The engine starts to act like running rich and can hardly run normal between idle and asking power.

I hope this helps.