After filling up at the pump, my '03 slk230 has to be cranked 2-3 times before starting-- stumbles a bit then smoothes out. This startup problem only happens when I fuel-up. The dealer couldn't find any codes, but as a stab in the dark replaced the charcoal canister. This had no affect at all on the starting issue. Any ideas what might be causing this??

 

Do you have the same problem doing a "pretend" fuel up. i.e. Stop, just remove the cap and replace but keep timing consistent with a real fill up.
Do you have the same problem doing a "pretend" fuel up WITHOUT removing the cap but keep timing consistent with a real fill up.?

The fuel system senses the pressure in the tank. I wonder whether this may be something to do with your problem.

Mileage? Service History? The fuel filter also includes a pressure relief valve which can cause similar problems. Filter usually OK to 100k but may be allowing vaporisation to occur due to fuel in engine rail vaporising due to lack of pressure in system and the heat coming from a HOT engine.

However, subject to the tests above i suggest you may find that it has nothing to do with the refuel but is a "hot" starting problem which is a totally different situation.

Stuart

 

you are relieving pressure in the tank when you remove the cap. maybe a fuelpressure checkvalve problem.