Lawn mower would be a 2-stroke burned smell since its burning oil as well as fuel.
Try this, on the weekend after your car has been sitting an extended period of time do you smell fuel? if yes wait longer, we want to be smelling almost no fuel before you begin the next part.
If you turn the key to on do you smell fuel now? if yes where?
Turn the key off for 1-2 sec then back on, does the smell get worse? Location?
Turn the key off and look at the location the fuel smell is strongest, do you see any wet spots? Have someone else turn the key to the one position, can you see where the fuel is coming from?
In doing the preceding steps you assume all risk inherit with handling fuel including getting it in your eyes, may want to wear goggles for the last couple steps. Do so at your own risk.