I have a 2003 E500 with a problem with the vapor recover system. Car sets a vapor recovery leak code. Car does not hold pressure in the gas tank. I smoke tested the system and the leak showed up at the vapor recovery tank vent to atmosphere. Not sure how the system is supposed to work but I think a check valve in the recovery system is bad and is not letting the system hold any pressure. I manually closed the vent and pressured the system up and it did hold pressure. Does anyone know how much pressure the vapor recovery system for this car is supposed to hold? Am I looking at replacing the vapor recovery tank to fix this problem?
Thanks John

Did you PLUG the vent hose OR activate the valve?

The system always vents EXCEPT when the system does it's leak check.

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Plugged the vent for about 15 seconds with my finger over the vent with a smoke machine pumping pressure into the system. Cracked the gas cap and I had pressure in the system. Looks like I will have to jump power to close the valve to get a good pressure check. And make sure power is going to the valve when the ignition is on. Thanks John