289cobra1

My r230 gets a check gas cap warning when stopped at red lights. The code is 455 evaporator emission system leak. I replace the evaporator canister. Drove the car 150 miles without an issue. Now the warning light is coming on again. I have replaced the purge control valve. Any ideas on how to correct.

kbob999

I've been down this road. It could be any place in the tank/evap control system.

Easy to get a new gas cap oring, or purge valve; harder to find the leaks at hose clamps, lines, or the charcoal canister. It could even be the fuel sender oring, or fill hose to the tank.

If you have access to SDS, you can start the car and run the 'tank' test to see if the system is holding vacuum. This will eliminate a lot of the potential causes. If it holds vacuum, it is not the tank and associated piping and hardware.

In my case, the vacuum line from the intake manifold to the purge valve had fallen out of the port in the intake manifold. Plugged it back in, tank showed vacuum was holding, and it was fine.
But that was after I chased the purge valve, gas cap, and all the easy stuff. Should have started with the SDS!

289cobra1

Thank you. I will check out what you suggested. It is strange that it occurs when i am stopped for a long stop light.

kbob999

That is when the engine is pulling the highest vacuum, and the system meets all conditions for proper sealing and purging.
It may not trigger when driving throttle open, or when cold start or refueling conditions occur.

Dhunch22

can you take a picture where this is and share so we can check it out? i have the same issue, reset the error and it comes back after about 100 or so miles.

kbob999

Go see this link: https://mbworld.org/forums/sl-class-...solutions.html

This is on the SL55, so it won't be the same for the non-supercharged SL500 V8.
Just follow the purge valve line that goes to the engine until you find where it connects.

Dhunch22

any idea where exactly to look on a '07 SL550?