After driving for a while, when I reach home and park my car, my wife always complains that the car´s emissions have a strong gasoline smell.

My father in law drove the car while I was away travelling on business and he told me he thinks the fuel-air mix ratio must be off.

My car has the lambda (emissions) light on, and the EVAP valve will be changed in a couple of weeks (waiting for the darn spare). Could this be causing the problem?

It could be the O2 sensors too, I don't think they have ever been changed since the previous owner did not have the work "maintenance" in his dictionary.

 

Is the check engine light on?

Do you have the codes if so?

Are you leaking any gas at all after fill up?

 

Lambda light is on, CEL is off.

I don't have the codes, but Volvo told me the EVAP valve has to be changed.

It happens at any time, not only after filling up.

 

The Evap Valve could be stuck open and causing the Gas smell.

It could also be a cracked rubber line by the Fuel Tank.

 

If it were a cracked rubber line by the tank wouldn´t I smell it when I fill up?

Right now I only smell it when the engine is running. Fill ups are fine...

 

Possibly. Also check ther small hose that runs from the Radiator area to the Rear of the car.
There is a valve next to the cooling fan. The hose runs to the back of the car check that. When the car runs that is for the self test to see if the tank system has a leak. Gas fumes will come out when the car is running and the Valve is working.

Also look on the engine and find the injectors. On the left side of the fuel rail see if you have a return line.If you do there will be 2 lines from the fuel rail. Check the return line for cracks.