E320 EVAP issue
 

Hey Everyone!

Bought a 2004 E320 for my wife and having an intermittent problem with the Gas Cap warning light coming on. By the time I got it into the mechanic the check engine light had come on and he said the error indicated was 'Gross Leak'. He changed the gas cap out but that hasn't helped with the gas cap error still coming on intermittently, however no check engine light again as of yet. The mechanic smoked tested the car and said there were no leaks. He also checked purge and vent valves and said that they held pressure. He felt that it was probably an issue with purge/vent valves or computer itself. He said that we could try replacing the vent valve carbon cannister combo, but it would be expensive due to the price of parts. I've identified a car similar to my own at pick-a-part place and am contemplating going down there to salvage it's carbon cannister and vent valve. Before I did that I wanted to check here and see if one of you knowledgeable folks might have any other suggestions on what might be going whacky here?

I had a similar problem with my old W210 - In my case the leak was the "regen" valve was dirty. Its the black square valve with the vacuum tubing in the engine room - also called purge valve. remove it and shoot some WD40 in it to clean it out. Let dry and install back.

You can remove the rear carbon canister and its venting valve to check for blockage - try operating the valve, if its sticky then smack it to dislodge any debris.