2014 MERCEDES ML350 3.5L - P0455 GROSS EVAP LEAK

Check engine light is on, found service code P0455 - gross evap leak. Code description mean that evap system notice there is a large emission leak. Most people want to put a gas cap on and pray for the best. Usually a gas cap doesn't repair anything. Best way is to smoke test the system .  On this specific vehicle, we activated the purge solenoid and found that even with the solenoid close, smoke was still seeping through. Usually with a bad purge solenoid there will also be rich condition. Do the proper check out so you don't replace unnecessary parts.