Gas Evaporator System Questions

[crashr]

Hi Folks,

I have done a lot of searching on the topic but can't find the answers I need.

First of all my car is a 1975 911 however I have a 3.2 engine in it.

The last few years I have noticed that I am getting a fuel smell in the cabin after the car sits overnight. I did some searching and most posts point to the fuel evaporator system. I started checking my hoses and noticed that many of them were fraid, dried out, and cracking. I would like to first replace these hoses but have no idea what kind of hose to replace them with. I couldn't find the braided hoses on Pelican. Can someone please recommend a type of hose that should be used?

Secondly, when the 3.2 engine was put in the car the charcoal box lines were never hooked up again. I am hoping that someone can tell me where on a 3.2 I could hook up these lines, keeping in mind that my charcoal box is in the rear of the car. I believe one of the small braided lines (which is in really rough shape) runs from the front expansion tank to the rear of the car. Can I just replace this hose and pull a new one through the car? The other two lines that go to the charcoal box appear to be larger hoses (however I don't have them). From diagrams it looks as though I should connect one to the back of the airbox, however for the other one I have no idea where to connect the pressurized line to the engine.

[HarryD]

Dennis,

You need to reconnect the lines. This drawing shold help you with the routing:

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:

[...]

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]
...

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

[crashr]

Hi Harry,

Yes I saw this diagram in a couple different posts that I searched. I guess one of my questions above was, On a 3.2 Engine, does #5 Line in your diagram above exist on the cooling shroud." I am not aware of where this is, can you comment?

I am also interested in what type of hose is suitable for replacement and where can i find it. I think I saw in a post that standard rubber hose is not good for this application.

[HarryD]

Dennis,

I am not very "expert" on the newer 911's. Hopefully someone who knows will step up.

I would think any standard fuel/vacuum hose would be ok. Check for gasoline fume compatibilty.

[RWebb]

the hose must be rated for fuel or fuel vapor - ordinary PVC hose is not good

so, go to a hose place not a hardware store


as a fellow 1973.5 911 formerly T owner, I also dunno about your new car...

[crashr]

Hi RWebb, I was hoping you would post as you seem to have some good knowledge in this space from what I could tell in my search.

I will check out a hose place this week to see what they have.

Any comment on how best to route the 2.7 Charcoal box, to a 3.2 engine?

[RWebb]

on my car, the canister is up front and the lines run inside the tunnel (that would be a lot of effort to add them post hoc)

on the '75 I used to have, the canister was in the upper RH side of the engine comp. but I don't recall how the lines to the front were run

if the existing line in the tunnel is not fastened, then you could use it to pull the new one

BTW - the trunk to tunnel connection IIRC goes thru the cabin above the pedal cluster

Good Luck

[Cooper911SC]

Hi Dennis,

Pelican sells the cloth braided German fuel and breather line by the meter. Sorry about huge link...I just searched on the site. You might call if you dont see your size listed as I'm sure they can get it from their supplier. You could also try local vintage VW suppliers/shops in your area. I have also purchased this style hose from them.

Pelican Parts - Automotive Parts and Accessories - Porsche & BMW


I used some of this line for the vacuum lines on my SC. It is ok for fuel.
You will need to verify the I.D. and lengths you need of each size. My memory is that the larger size is somewhere around 10mmID and 13MM OD.

Good luck with your project.

Cooper

[cary]

Ditto on Cooper's input.

[crashr]

I have a question about the above picture showing the venting system. Where on a 3.2 can I find a line that will provide air to the charcoal box. On the 2.7 it came from the shroud but that hole doesn't seem to exist on a 3.2.

Thanks,
Dennis

[grizzfan]

This is pretty complex for a guy from Montana! I have a '73 911T with a '76 2.7 in it; the charcoal cannister is up front next to the battery. I also have fuel smells in the cockpit. I wonder what the problem could be: a) no "fresh" air from the engine fan; b) the cannister is 34 years old and needs to be replaced; c) ???

Sorry to step on your post, but seems related to the overall problem.

Tom

[RWebb]

canister is good until it bursts unless you got liquid fuel in it

replace all your hoses in the trunk & check tanks under cowl & fender for cracks before doing anything else

do a search - you cannot use regular PVC hose from a hardware store

[HarryD]

Originally Posted by grizzfan

This is pretty complex for a guy from Montana! I have a '73 911T with a '76 2.7 in it; the charcoal cannister is up front next to the battery. I also have fuel smells in the cockpit. I wonder what the problem could be: a) no "fresh" air from the engine fan; b) the cannister is 34 years old and needs to be replaced; c) ???

Sorry to step on your post, but seems related to the overall problem.

Tom

Tom:

For your car, Grady Clay posted this which should help you to see how it "should be".

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

[crashr]

Can someone comment on where a 3.2 charcoal box gets its fresh air supply from?

[James Brown]

look in the PET for your 3.2 (like a 90 Carrera) to find what hose to hook up to. Hard to find the CIS connections on you 3.2. You will have to marry both systems together to make it work but it's not that hard, just need the correct source of vacuum and your in business.

[crashr]

I have done that. Unfortunately for all the 3.2's from 86-89, PET only shows the carbon canistor which has 3 inlets. One must come from the trunk, the other goes to the back of the airbox, its the 3rd which provides air into the carbon canister that I am curious about.

[James Brown]

I'm thinking one is a air inlet, one from the airbox, and one from the tank. Not sure which is which, sorry.

[crashr]

Hi James,

I agree one is the air inlet, the question is, where does the air inlet come from?

[James Brown]

Oh, its just open to the atmosphere.

[crashr]

Really? PET shows a hose going to it. Where does this hose lead to that just opens to the atmosphere?