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1984 500SL (RHD) 160k miles
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188 Posts
Discussion Starter #1
OK I've had some strange problems with this car, but this one takes the cake.

When driving with either the driver or passenger side windows down the cabin quickly begins to wreak of petrol. It's not just a faint smell, it really stinks! The wife is not too happy. It's nothing to do with the internal ventilation system, as that doesn't smell at all. So either:
1) The smell is coming from the engine bay, but somehow completely bypasing the ventilation system that draws air in above the bonnet..
2) The smell is coming from thefuel tank area, and air is somehow flowing against the oncoming airstream to carry the smell into the cabin.
With the windows down the air is being drawn out of the cabin by the passing airstream, so 2) is probably the most plausible explanation. I had a look at the tank when removing the boot/trunk bulkhead and it all seemed fine. Will remove again and take another look.
Anyone else experienced this bizarre problem?
Cheers.
 

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W221 & Audio Moderator
2013 S550
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10,978 Posts
When I had a similar problem with my 450SL, a "C" shaped section of fuel line had been omitted in a repair before I bought the car. The main fuel line had been folded over and crimped. While the engine got enough fuel to run, the line developed a leak at the crimp, and the strong smell occurred. Finally, the line ruptured completely, and a significant amount of fuel was pumped out before the fuel pump shut itself down.

The first time it occurred, it was in the dealer's parking lot. The dealer replaced my fuel line, but not the "C" shaped section; he installed the new line exactly as the old one had been. Three weeks later, the new line ruptured as well - but it leaked and smelled just as the old one had, for a time before the complete rupture.
 

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1979 450SL UK spec
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1,442 Posts
I had this a few times, it turned out to be my fuel cap was not fully engaged on both tangs. Mine really needs to be pushed on very firmly to ensure both sides engage, otherwise fuel can escape and strangely the fumes head for the cabin.
 

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1988 560 SL
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652 Posts
I had such a smell -- not super strong, but still. It turned out to be fuel leak that I had repaired when I had the fuel injection system replaced.

Now: fuel smell gone.
 

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Registered
1984 500SL (RHD) 160k miles
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188 Posts
Discussion Starter #7
Thanks guys. Have looked at the petrol cap and it seems fine, rubber seal in tact etc. I think I have one of those emergency ones around so I might try that and see if there's any difference. I checked all pipes behind the trunk wall and all are ok. Will check fuel pump/filter pipes but had this off recently and there weren't any leaks. Before anyone metions it, I also checked the sender unit and that also seems fine.

Will report my findings.

Cheers.
 

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1975 450SL
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244 Posts
The hoses in the engine compartment around the fuel rail and where the injectors clamp to the rail are all prone to leaking when the hoses get old. When this has happened on my car the smell was evident in the cabin even with the top down.

My guess is that the air goes in the front of the engine compartment through the fan and radiator and comes out the back of the hood (bonnet) and into the side windows. There have been threads that discussed the deterioration of the seal at the back of the hood and how it relates to smelling engine smells.

I would take a good look at all the hoses in the engine compartment right after starting the car and look for weeping or leaks.

Good luck.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,510 Posts
The hoses in the engine compartment around the fuel rail and where the injectors clamp to the rail are all prone to leaking when the hoses get old. When this has happened on my car the smell was evident in the cabin even with the top down.

My guess is that the air goes in the front of the engine compartment through the fan and radiator and comes out the back of the hood (bonnet) and into the side windows. There have been threads that discussed the deterioration of the seal at the back of the hood and how it relates to smelling engine smells.

I would take a good look at all the hoses in the engine compartment right after starting the car and look for weeping or leaks.

Good luck.
K-jet...not D-jet.
 

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1977 450SL
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257 Posts
If there are no fule leaks evident under the hood you might check the hoses going to the charcoal canister.
Just a guess but the hoses on my 77 were pretty deteriorated when I got it.
 

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1984 500SL (RHD) 160k miles
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188 Posts
Discussion Starter #13
if napalm smells anything like 98 super unleaded then i probbaly wouldn't mind it any time of day, it's the wife that's the problem, and also the occasional desire to smoke a cigarette out of the open window smells like it could be dangerous.
 

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1984 500SL (RHD) 160k miles
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188 Posts
Discussion Starter #14
hi guys,

just to update, it was the gas cap after all! the spring-loaded thing had become dislodged and so was not pulling the cap closed properly. jamming a screwdriver in the slots I managed to get it into place again and voila: no more petrol fumes!

once again, this forum rocks.

thanks guys.
 
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