2004 E500 4-Matic (67k miles)

Been playing whack-a-mole with the EVAP system on my E500 once it started throwing a P0446. I've done the easy to get at stuff...the gas cap and the purge/MOT valve under the hood. I understand that the charcoal canister and shut off valve are in the rear wheel well, but is it on the passenger or driver side? With the age of the car, I should probably check all of the lines and hoses for leaks but don't know where or how those are routed once they disappear from view around that box under the hood around the firewall.

 

Behind right, rear fender liner.

 

Bit the bullet and spent the money for the new shut-off valve, O-ring and wiring adapter and....it's still throwing the P0446. So that leaves a leak or computer problem. Not sure what the bad computer symptoms would look like. I'm not encouraged that I can clear the code, restart the car and it's all good, but as soon as I shut it off again and restart, the code comes right back, even though I filled the fuel tank. I had thought that the pressure test it runs for this system was only supposed to work below 3/4 tank fuel level.

Since it looks like a smoke tester purchase is in my future, anyone have any suggestions on which one to get (or avoid). I've seen some that require an air compressor. Anyone know what a safe PSI would be for testing this? I'm thinking that using the setting I would to fill my tires would be ill advised.

 

Hi Ivan.

I did the exact same thing you’ve done. Changed the purge valve then replace the shut off valve, O-Ring and new harness. Still get P0446.

were you able to resolve the issue?

question about the shut off valve. Should there be any hose attach to it or it’s supposed to be left open?