next time you can smell it hardcore strong, open the hood and the trunk and see if its stronger in either places.....
The fuel tank on the Y50 is located on the underside of the car right above the differential, for referenence right below the rear seat...
If you can smell it more on in the trunk, then its coming from the fuel tank, if its stronger when you open the hood, then its coming from something in there.. Just because you cant see a leak does not mean there isnt one...
There could also be something messed up in your evap system. basicaslly what that does is take excess fuel vapors from the tank and recirculate them back into the intake.. Common on any car from 1990.
quote from the 2006 m45 service manual
FSM wrote:The evaporative emission system is used to reduce hydrocarbons emitted into the atmosphere from the fuelsystem. This reduction of hydrocarbons is accomplished by activated charcoals in the EVAP canister.The fuel vapor in the sealed fuel tank is led into the EVAP canister which contains activated carbon and thevapor is stored there when the engine is not operating or when refueling to the fuel tank.The vapor in the EVAP canister is purged by the air through the purge line to the intake manifold when theengine is operating. EVAP canister purge volume control solenoid valve is controlled by ECM. When theengine operates, the flow rate of vapor controlled by EVAP canister purge volume control solenoid valve isproportionally regulated as the air flow increases.EVAP canister purge volume control solenoid valve also shuts off the vapor purge line during decelerating andidling.PBIB1631E
Attached is a picture of a diagram of the evap system..