Fuel Odour Problem

Curing the Fuel Odour Problem in the 964 Trunk

A common problem with the 964 series is the development of a strong fuel
in the trunk area. Porsche has even issued a technical bulletin (29401 MAR 94)
to cover this issue. The most common cause is a problem with the design of the
fuel filler neck. The original part has been superseded twice with 964 201 043
03 and the most recent 964 201 043 06. It appears that the original design would
allow for a warping at the top where it meets the cap and possibly for cracks
to form in the filler itself.

The picture below shows some of the differences between the original 01 and the
06 version.

The newer part shown at the bottom is substantially stronger, especially at the
top where it meets the body. There were also some improvements that are visible
when looking at the top (they don’t show up well in the picture). These may make
have been done to handle the fuel quicker, but that is just a guess. The new
part is on the left.

The installation of the new part is not difficult and is rated by Porsche as a
half-hour procedure. It took the two of us a little over an hour, but we took
some of the time with just figuring it out and taking the pictures.

To prepare you should have your fuel tank below full, mine was about 2
gallons down from full, which was ok, but to make it easier you might want it to
be closer to half. It would also help to have a large circlip remover, but it is
not necessary.

The first step is to remove some of the carpet in the trunk area to expose
the fuel filler area. You might want to remove all of the carpet now and clean
it. The smell will remain in the carpet for a while, so you may not be able to
tell if you have fixed the problem right away. You will also want to open the
fuel filler door.

This is what you will see in the trunk. The filler is attached to two hoses,
the lower one for fuel to travel to the tank and the upper for air to be
released from the tank.

You will want to place some rags below the filler just as we have done to catch
any fuel that may leak. Because the tank was close to full there was some fuel
in the hose that attached to the filler.

You will now want to loosen the clamp for the top (air return) hose. Grab the
hose and just wiggle it off. (We decided to reuse the clamps since they looked
ok.) Next loosen the clamp for the bottom hose. Here we had to carefully lift
the lower hose once it was free because it contained a little fuel. The picture
shows the top (air return) hose removed.

Once the hoses are disconnected you can turn to the filler neck. The filler is
attached by a large circlip.

This can be difficult to remove without the right tool and it took us the most
time in the project. A large circlip remover would help here. What we did was to
use a thin blade screwdriver to pry up an end and get it out of its groove. Once
an end was clear you could work it around prying as you go. This was easy once
we had the technique.

With the circlip removed you will see a large plastic ring.

Note where the wider part was located because you will want to fit it in the
same way later. It should fit between the posts for the screws (the picture
shows it off by 180°).

Next there is a rubber gasket. The filler will slide off the gasket (which
will remain in place) by pulling and gently rocking the filler from inside the

This is what you will see when you have it out.

Get the new filler tube and slide it back up the hole. Make sure you have the
gasket in place and then put the large plastic ring back the same way it was
before. If you get it wrong you will block the drain hole for spilled gas, so be
sure to put the wide part up between the posts.

Next you have to put the circlip back on. We were able to get it around the
top of the filler then push it down until it clicked in place. If you don’t
think you have it in the groove, keep the ends in front and you can easily look
down and see if it is in place. It is important to ascertain that the circlip is
fully seated in the filler neck grove as that is the sole mechanism for
retaining the filler in place.

Next reattach the hoses and clamps and you are done. Be sure you don’t over
tighten the clamps. You might have noticed when you took them off that they are
just tight enough to stay in place.

That’s it. The smell should go away once you clean your carpet because it
tends to retain the odour. If this doesn’t work then you might want to check the
gasket on your cap because the rubber tends to shrink with age. Other things to
check would be the condition of all the hoses connected to the fuel tank and
their connections and lastly the tank itself.

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