NorseWagon

Got the Check Engine light this morning. Never seen it in 3 years of owning the car.

About once a month I get a big red Check Fuel Cap light, but wrote it off as a loose microswitch or some such thing.

Did a search on the forum for similar problems, no cigar.

Any ideas, or does anybody have a list of what would cause the Check Engine light to illuminate..?

(All services and maintenance has been done, last trip to the MB dear 2 months ago)

ozusa

you can buy a new one, or try spraying a little silicon spray or a small quantity of some other lubricant, on the seal ring on the cap. (light blue ring on mine).

The engine light / fuel cap warning is coming on because there is a leak in the EVAP system. That is probably caused by the fuel cap.

The most common cause of an EVAP leak, and hence pollution, is an incorrectly sealing fuel cap, that's why Mercedes give you the red warning because it is the best, simplest, bet. (It could still be something else.)

ozusa

probably in the range P0440 or P0459

If it is not in that range, than it may have nothing to do with the fuel cap.

NorseWagon

Aha, there could be a connection then...?

If indeed the seal on the fuel cap is bad, then the light should be on every day, not just on for 2 minuttes, then go off, and only twice a month...?

Will take a close look at the cap, try the silicone trick and hook up a diagnostic code reader.

Thanks for chipping in.

ozusa

the seal will be good enough one day, then not so good another. One day you'll refuel and it will seat just right. Next time it won't. Eventually the seal may go completely.

This happened on mine about 4 different times. I'd simply remove the cap and reseat it and it would be OK for a few weeks.

Eventually I got fed up and lubricated it with silicon. It hasn't happened for a year now.

The check engine light should go away after a few days of no red fuel cap warning. If it doesn't, the cause is something else.

Vander

Try replacing the fuel cap first, if that doesn't fix it than more than likely you have a vacuum leak in the evap system.

NorseWagon

Good advice, thanks.

Will replace the fuel cap as soon as I can find a replacement and have a guy come to the house on Monday to read the error code.

Will report back.

gaazmon

You could fall into this:

https://mbworld.org/forums/e-class-w...1-e-class.html

NorseWagon

Aye, hope not..Been looking for fuel leaks over the years, but no cigar, fortunately.

Bought a new fuel cap on ebay, $44 including tax and shipping.

Hopefully that will solve the problem..

The car ran out of warranty 2 months ago, hopefully it will behave for a while..

gaazmon

i changed my cap and seals on the tanks and no dice still came up. gas smell when more than 3/4s of the tank is full too

NorseWagon

Looks like you got the leak..

Expensive fix, or still covered by the recall?

gaazmon

Recall for fuel sending units was only for the E55's

Ya it's started to pop up more and more on the w211s on this forum. First mostly the AMGs but now some of the regular variants as well

NorseWagon

Do that every time I fill the tank, but the red light still comes on from time to time and funny enough, only when the car is not moving, say waiting at a red light.

gaazmon

how interesting. mine goes away when i'm stopped and comes up again once the car starts moving

NorseWagon

Gremlins for sure, or Homo-Trons (Little Gay Elctrons running around f..... with every system on the car:-)

Got my new gas cap today, OEM for sure, if I see that red fuel cap light again, followed by the check engine light, I just lost $44.00.

(Should have tried silicone grease first to lube the seal as mentioned above, but was trigger happy and just ordered the new cap.)

NorseWagon

Soo, the red Fuel Cap warning light is back, and it set of the Check Engine Light.
Guess I wasted $44.00 on a new fuel cap. Called my indy mech, he is going to check MB service bulletins for more info on the problem, still tempted to try silicon grease on the fuel cap seal: If that fixes it, it would be a "no-cost" item.

Any other ideas...?

Can Drive 55

Add me to list of those with this exact problem. Red alert for gas cap and now check engine light. I am going to see if I can get the codes read and then I will post the results. Good luck.

gaazmon

https://mbworld.org/forums/w211-amg/...all-bombs.html

Alwaysthere

Me too on an 08 ml63.