Help…Fuel Smell…What is this?

[trentwat]

My car came out of the body shop a couple months ago (pic below). Upon re-assembly, something might have been missed. When I first fill up the car and drive, there is an occasional fuel smell. The shop is addressing a punch list, including this item. They confirmed the hoses on the vapor expansion tank were replaced, but they are not sure what the item is where a hose would connect coming out of the body (circled in red), so they capped it off. Any idea what this is?

[Hi_Fi_Guy]

See this thread:

Renewing Fuel Evaporation System
https://forums.pelicanparts.com/porsche-911-technical-forum/1114184-renewing-fuel-evaporation-system-70-911t.html

[HarryD]

You are missing a connection in the black vapor tank. Search for the terms emissions and fuel. Mr Grady Clay has number of posts on the topic.

This post from this thread (Fuel tank venting system question) may be helpful:

Originally Posted by Grady Clay

The evaporative emissions system is actually very useful
and worthwhile to keep in working condition. First and
very important, your 911 doesn’t constantly smell of
gasoline. If you are missing the charcoal canister, it
is common to many German cars of the era. Just tape
over the VW logo.

Here is the diagram for ’69-‘73: “

"
© Dr. Ing. h.c. F. Porsche A.G.


1) Expansion chamber [the black box under the cowl
on the driver’s side]
2) Vent chamber [behind the LF headlight]
3) Activated charcoal container
4) Engine fan shroud
5) Pressure line from fan to activated charcoal container
6) Purging line from charcoal container to engine air cleaner

Note the 13 connections around #1 and the fuel tank. This
clear (now brown) hose typically shrinks and comes off the
fittings causing gas fumes in the trunk and cockpit


Here are the locations in the 911.
“
"
© Dr. Ing. h.c. F. Porsche A.G.


With CIS the system was simplified somewhat.
“
"
© Dr. Ing. h.c. F. Porsche A.G.

1) Fuel tank
2) Expansion chamber [LF fender]
3) Activated charcoal filter [a reservoir for the fuel vapors]
4) Cooling fan shroud with hose connector [source of air]
5) Hose from cooling fan to activated charcoal filter [supplies
air to the charcoal]
6) Hose from activated charcoal filter to air filter [carries
the fuel vapors to the engine to be burned]
7) Engine air filter
8) Return hose connecting the fuel tank to the expansion
chamber [this clear (now brown) hose typically shrinks
and comes off the fittings causing gas fumes in the trunk
and cockpit]

This diagram shows CIS but the system is the simular for
MFI and carburetors from ’69 as above. The two tubes
in the tunnel are #5 and #6.


It is worth having all this stuff because some day you (or a
future caretaker) just might be required to have it functional.

Best,
Grady

[Discseven]

Nice all-black Trent.

[trentwat]

Originally Posted by Discseven

Nice all-black Trent.

Thanks, Karl!

[trentwat]

Thank you, Brian & Harry…I too started digging through diagrams last night…looking at the photo from the body shop, I now see where a hose would connect on the tank at the top and to the hard tube coming out of the body…highlighted by red circles in my new image…

…any idea where other end to the hard tube terminates (circled in green)? Looking through other posts, some of these hoses in this system seem to be in the frunk; car is still at the shop, so I can’t just go to the garage.

[midyearallyear]

Just acquired my '74 911 last week, and upon fillup, the car smells strongly of gasoline for about 30 minutes. I had no idea what was going on, and randomly found this forum! I have no idea what is what, but I at least now know it isn't normal.

[HarryD]

Originally Posted by midyearallyear

Just acquired my '74 911 last week, and upon fillup, the car smells strongly of gasoline for about 30 minutes. I had no idea what was going on, and randomly found this forum! I have no idea what is what, but I at least now know it isn't normal.

Welcome to our forum. Lots of expertise here. We like to see pictures of the cars. Add a location to you profile so we can see if there is anyone nearby who can help.

There are lots of pictures showing the system on numerous threads. Check to see of all the parts are present and the hoses are connected. If you post some pictures of the trunk showing the fuel tank, the area near the master cylinder and inside the left front fender we may see some clues as well.

Common failures are separated/deteriorated hoses, cracked/missing vapor box under the cowl, failed vapor tank in wheel well.

These threads may be helpful:
https://forums.pelicanparts.com/porsche-911-technical-forum/801970-sorting-out-my-new-toy-fuel-smell.html

https://forums.pelicanparts.com/porsche-911-technical-forum/644156-holy-crap-moment-fuel-smell-source-after-fill-up-goes-away-after-30-miles-idd.html

[spuggy]

Originally Posted by midyearallyear

Just acquired my '74 911 last week, and upon fillup, the car smells strongly of gasoline for about 30 minutes. I had no idea what was going on, and randomly found this forum! I have no idea what is what, but I at least now know it isn't normal.

Seems likely you may have a cracked hose, missing equipment and/or a leak. Might be an idea to take a look. When I got my '77, a lot of that was missing - overfilling resulted in gas under the car. Not ideal. You can probably greatly reduce the issue just by being careful not to overfill.

First, filling the tank correctly; "they're not like other cars", LOL...

If you use the pump like anything else, it'll probably click off all the time, even at very slow pumping speeds. Using the pistol grip upside down (so the hose is at the top) looks odd, but helps a lot. Something to do with turbulence in the filler.

Play with the trigger to work out how fast you can actually pump gas before it clicks off - ie, if tank is near empty and it clicks off, you're probably going too fast. Somewhere around 1/2 or 2/3 trigger seems to work well.

Then, once you've found the sweet spot, believe the pump when it thinks the tank is full and don't overfill. You'll probably hear gas swirling up in the filler neck right before it switches off.

And it's good to be aware of gas smells. Entirely possible for pressure lines to develop a tiny leak leading to a fine spray and a whiff of gas smell in an enclosed space. These can be the very devil to find, as it evaporates pretty quickly if the spray was fine enough - and it all looks dry when you go looking for it. Until the line eventually ruptures, then they're very easy to find...

[PeteKz]

My bet: Expansion chamber. It's #1 in the diagram above. Stick your nose up in there to sniff. At this age, they all are cracking. Happened to me a couple years ago.