Recently I started to use heater, I noticed very strong fuel odor from the air vent when I turned on heater, it went away if I turned off heater.

Does this indicate I have fuel leakage under the hood? any ideas?

Thanks

__________________
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.