Hyundai Repair: Fueling system, fuel cap, gas cap

Question
When I remove the gas cap to refuel the engine stalls and is difficult to restart.

Answer
Hi, Tim.  I'm going to presume you mean that you have difficulty starting the car after refueling.  In most cases, this is caused by a stuck open purge control valve.

In the case where you do indeed you remove the fuel cap to refuel the car while the engine is still running, the diagnosis is still the same, as this will allow a rush of air or fuel vapor into the engine through the stuck open purge control valve.  But I'll also recommend that you not do this.  For safety reasons, it's against the law to refuel the vehicle with the engine running.  Additionally, depending on whether the evaporative system is being checked at the time, this practice can cause the check engine lamp to come on.