When I start the car, there is a very strong smell of gas in the cabin. What is causing it? Is it expensive to fix?
A few helpful tips:
Make, model, and year of car.
When did it start to occur (e.g. after fill-up?)
Otherwise, it is impossible to diagnose.
Based on this limited information- I’d suggest that you have a malfunctioning EVAP canister or fuel cap. Regardless, it needs to be fixed. Good news- most emissions systems are covered under a separate warranty thanks to the US Gov’t that covers these items even on higher mileage, older cards.