fuel smell by gas tank when it's full or nearly full

ronnieg · Post by **ronnieg** » Wed Dec 16, 2015 6:15 pm

Whenever I fill the tank, I consistently smell gas fumes from the rear of the car, near the filler. after I drive for a while and the level recedes, it no longer smells.....only when it's nearly full or close to full.

The cap looks to be tight.

I do not see any leaks under the car.

Thoughts on where the fumes might be coming from? and how to get to it/them?

635L6M3 · Post by **635L6M3** » Wed Dec 16, 2015 7:21 pm

There are 3 vent hoses coming out of the filler neck going to a canister in the trunk. They wear / rot away after years.

Also, there is a gasket by the fuel pump / fuel level sender, which could be bad. Located under the trunk carpet.

Probably a fill neck gasket or something as well, but I'm not sure.

http://www.realoem.com/bmw/enUS/showpar ... Id=16_0096

http://www.realoem.com/bmw/enUS/showpar ... Id=16_0014

olympia57 · Post by **olympia57** » Wed Dec 16, 2015 7:21 pm

Check that all three rubber vent lines from tank to expansion chamber are intact , correctly secured and not split /perished.
Check and follow the actual vent to atmosphere line that runs out of the expansion tank down and round to the tow point behind the spare wheel well.
http://www.realoem.com/bmw/en/showparts ... Id=16_0074
Obviously check the tank for signs of weeping from any rusted sections . I found mine had several pin holes above and below the centre joint of the tank.

Good luck
Don

EDIT
The actual vent line may differ from EU to USA spec.

GRNSHRK · Post by **GRNSHRK** » Wed Dec 16, 2015 7:23 pm

There are 2 possible sources of this gas fume "leak", presuming that your tank itself isn't leaking, around the filler neck, for instance

By the filler neck but accessable from the right hand side of the trunk (boot) there are 3 braided vent/return lines that often get brittle over time and start to weep

Also, under the trunk mat you will find an access panel to the in-tank fuel pump, which can also be a source of leaking

I would start investigating in these 2 locations

slofut · Post by **slofut** » Wed Dec 16, 2015 10:08 pm

olympia57 wrote:Check that all three rubber vent lines from tank to expansion chamber are intact , correctly secured and not split /perished.
Check and follow the actual vent to atmosphere line that runs out of the expansion tank down and round to the tow point behind the spare wheel well.
http://www.realoem.com/bmw/en/showparts ... Id=16_0074
Obviously check the tank for signs of weeping from any rusted sections . I found mine had several pin holes above and below the centre joint of the tank.

Good luck
Don

EDIT
The actual vent line may differ from EU to USA spec.

Even if they look great (as did mine) they can still weep fumes. I blamed it on everything else first, finally changed those three hoses and like magic ...no more dreadful smell.

ronnieg · Post by **ronnieg** » Wed Dec 16, 2015 10:47 pm

OK, thanks to all!. I'll check them all out and report back.

Merry Christmas!

Pod · Post by **Pod** » Fri Dec 18, 2015 11:50 am

Check there's no corrosion around the three pipes where they enter the tank. With a full tank, I've found petrol may seep out here as you corner.

sansouci · Post by **sansouci** » Fri Dec 18, 2015 6:51 pm

Realoem shows a lot of 6x11mm and 8x13mm fuel hose. How much will I need to re-plumb my aging '84 633? Who's got the best stuff? I've seen a lot of Conti and CRP...Is that short for CR#P?
--Ken

Ralph in Socal · Post by **Ralph in Socal** » Fri Dec 18, 2015 7:11 pm

Buy German (Conti) not Chinese (CR*P). You need 8mm for the majority of it so buy 3 meters (a little over 9 feet) and it will cover what you need for feed lines and return lines. 2 meters might be too tight so I aim for a little extra as you want your lines to have room to move. The feed line from the tank to the fuel pump is 12 mm and you will need 2 feet (less than 1 meter).

The 6X11 is used for the vent lines and you'll need about 3 meters of that as well.

Ralph

Steve M6 · Post by **Steve M6** » Fri Dec 18, 2015 8:52 pm

For some reason BMW used original fuel lines having a braided fabric reinforcing. I have had them all fail by seeping gas on both of my 6-series cars, a 5-series E28, and BMW motorcycles.

If you can see any braided lines, they all must be replaced. You will also need about 8 new worm-drive clamps. I replaced one line at a time so the original routing to the cannister in the trunk below the package shelf was maintained.

bpoliakoff · Post by **bpoliakoff** » Sat Dec 19, 2015 2:47 am

Pod wrote:Check there's no corrosion around the three pipes where they enter the tank. With a full tank, Iâ€™ve found petrol may seep out here as you corner.

Beyond â€œseepingâ€

Pod · Post by **Pod** » Thu Dec 24, 2015 10:06 am

Absolutely agree. Yours had gone past seeping! However, I have found that when corrosion is not too far advanced, this can only be seen with a full tank and wetness apparent around the pipes. As soon as fuel level drops, all looks well .

ronnieg · Post by **ronnieg** » Tue Jan 05, 2016 5:56 pm

Replacing the three hoses appears to have worked. no fuel smell this time. one of the hose clamps was loose, which could have been the whole problem, but I replaced the three hoses while at it.

thanks to all who posted helpful advice and pics.

Happy New Year.

bigcoupe.com

fuel smell by gas tank when it's full or nearly full

fuel smell by gas tank when it's full or nearly full

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Re: fuel smell by gas tank when it's full or nearly full