E320 124 Fuel tank vacuum (petrol)

[kth286]

Hi guys

Could not take tank filler cap off due to vacuum build up when tank was near empty. Cap subsequently removed.

Found car was in limp-home mode due to sensor fault code not being cleared.

Cleared fault.

Tested EVAP system and found purge valve to pulse OK when engine up to working temp.

My subsequent thoughts lead me to question whether purge valve that feeds petrol vapours from charcoal canister into engine is prevented from operating when car is in limp-home mode, to prevent further degradation of engine performance.

Does anyone know if purge valve is prevented from operating in limp-home mode ????????????

If so, where can I find a description of parameters for engine operation when car is in limp-home mode ?????????

[kth286]

Anyone not been able to remove their gas tank cap ?????????

If so what was the problem ?????????

[Michael K]

A few years ago, I had a really hard time getting the fuel cap off our 1994 E320. It turned out to be a broken gas cap. I forget exactly what was wrong, but it was something about the alignment of the white plastic part in relation to the black cover. I pushed and pulled all different ways, and it came off eventually. I put on a new one, and it was all good.