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Discussion Starter #1
I read through a few posts on here of similar issue, but no resolution. Has anyone found what causes this? This users post is almost exactly like my issue. Only happens when near 32 degree F, when using the heater, smell originates from engine bay somewhere, no leaking I can see. I tried to replicate the smell when its warmer with heater on, but no gas smell.

"I parked my car outside and the weather was like 32 degree in Fahrenheit. I got in the car, started it up, and turned on the heater. Instantly I smelled gasoline through air vents. My first thought was vehicles went by but the smell got stronger. I shut the engine down, popped the hood up and I could smell gasoline in area somewhere between fuse box and engine block! I let the engine ran again without turning on the heater for about 5 minutes and everything was back to normal, I could crank the heat up! It happened the same next day...

On the weekend, I parked my car inside garage and the weather was much cooler. I started the engine and cranked the heater on, everything was normal. Unfortunately, the cold weather was gone and I could not replicate the issue again.

Anyone knows what would be the issue? I have a feeling that my mechanic at the dealer won't be able to find out anything as the weather is now warmer!

This is very odd problem! I own this MB only 2 weeks and I bought it as used one, thanks.
 

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Although you really shouldn't smell gasoline inside the vehicle the engine does run richer upon startup in the cold. Also many northern US regions switch to Winter fuels to help reduce emissions in cold dense ambient air which are innately more odorous. And as most of us do, we startup the vehicle inside the garage (just after opening garage door) and the relatively cold/dense air within and more so from outside when the door opens tends to concentrate those rich fuel odors around the vehicle which in turn can get into the vehicle to a degree via the cabin air inlet.

Also keep in mind that gasoline tanks are vented so as to break any vacuum and facilitate flow, as well as accommodating fuel expansion and thereby pressure relief.
 

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I recall a couple problems with the HPFP (high pressure fuel pump) required for the DFI (direct fuel injection) motor leaking. It seems like this was a problem with seals rather than the pump itself. This could be dangerous. Take it to the dealer. Since this isn't a common problem your dealer may be ignorant. Be forceful with your complaint. Insist on warranty or good faith repair.
 

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Discussion Starter #4
The few nights its been near 32f is when its happening. And I'm parked outside. Its definitely not just from start up because it smells everything I stop at a stop light all the way home, a 25 minute drive.
As far as we shouldn't be smelling any fuel smell inside, the heater has to suck air in from somewhere when recirculation is not on so I assume it's from up front of the car somewhere.
I agree Wayne, I came across some info that it could be the HPFP seal leaking. My theory on why it only happens when cold out is that the seal shrinks in the cold and expands when its warmer out. Like last night was 40 out when I did the exact same drive home from work and there was no gas smell at all.
 

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Sounds like you have your answer and as Wayne cites it's a critical safety issue so push that with your dealer to repair/replace under warranty.
 
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