Fuel tank venting system question

[daniel911T]

Hey everyone,
Ok, I'm still working on my '69T. The car stinks so strongly of gas that I'm actually a bit afraid to drive it. Last time I had it out I was getting light headed and nauseated!

I have been trying to figure out the tank venting system, with little luck. On the parts diagrams I've seen, the early cars do not appear to have charcoal canisters, and slightly later ones have the canister and an expansion tank. I've looked at diagrams for the early cars, and none of them look anything like mine.

One of the biggest issues is that my car does not appear to have a line, or pair of lines, running to the engine. I know these things generally vent to the air cleaner. I have the obvious issues of several connections open to atmosphere, but it seems that all this stuff should be hooked up to something.

Does anybody have a good diagram of a '69 tank venting system? What is the flow actually supposed to look like?

Here's what I currently have:



Thanks for the help!

Dan

[KTL]

I'm not familiar with the factory routing, but I can offer some additional advice for things to check. Assuming you've got carburetors, be sure to check the accelerator pump housings for leakage. My Webers had a substantial leak that was contributing to the massive gas smell (race gas to boot, which I hate the smell of even more) outside the car. After I found that, the garage didn't smell like gas any more. And this is with my fuel cell having nothing but a simple vent hose venting to atm.

The smell still resides in the cabin and i've traced that to an aging braided stainless main fuel supply line. No signs of liquid leakage that I can find. However the braid must be hiding it. So that line is now removed and will be replaced.

[daniel911T]

Originally Posted by KTL

Assuming you've got carburetors, be sure to check the accelerator pump housings for leakage. My Webers had a substantial leak that was contributing to the massive gas smell (race gas to boot, which I hate the smell of even more) outside the car. After I found that, the garage didn't smell like gas any more. And this is with my fuel cell having nothing but a simple vent hose venting to atm.

I do have Webers, and I did just rebuild them. The right side of the engine bay does smell more than the left. It's probably a good idea to check out the acc. pump housings. It's pretty easy and cheap to tighten some nuts.

Originally Posted by KTL

The smell still resides in the cabin and i've traced that to an aging braided stainless main fuel supply line. No signs of liquid leakage that I can find. However the braid must be hiding it. So that line is now removed and will be replaced.

The smell is worst in the cabin, but I assume it's coming from the trunk back into the cabin. I thought that all the fuel line through the cabin was solid metal tube. I have already changed all the rubber tube on the car. Is there a union in the cabin that could be leaking?

Thanks!
Dan

[Grady Clay]

Dan,

Was your car individually imported or did it come to the USA via the Importer (P+A) & Dealer network?

That sorta looks like someone installed a charcoal canister to ‘comply’ but it isn’t connected properly.

For a start and for your safety, vent everything to outside the car.







If you are willing, you can run a hose (~16 mm) from the vapor reservoir under the cowl alongside the passenger side of the tunnel, through the vertical panel under the RR seat and up into the engine compartment. Make this one continuous hose. You can mount the charcoal canister on the rear shock cross member.



You need to see what vent/breather fittings are on the rear of your air filter assembly.

Are there any air ‘ports’ on your fan shroud? If memory serves me, there is a plastic plug through the fan shroud just inboard of cylinder #1. If so, you can use that as an air supply.

The system works by the fuel venting fumes come to the rear and are (mostly) stored in the charcoal. When the engine is running, the (slightly) pressurized air from under the fan shroud goes through the charcoal and picks up gasoline vapor. The air/vapor mixture then goes to the air filter assembly where it is mixed with the combustion intake air.

It is critical that the proper hose is connected to the correct port on the charcoal canister. Get a new charcoal canister -- newish (German?) junk car should be inexpensive.

Best,
Grady

[LJ851]

I cant help with your vent hose diagram but i have owned and currently own several cars/motorcycles that have carbs with fuel tanks vented straight to atmosphere in my basement garage . The only time i smell fuel while driving or when they are parked is when there is a liquid fuel leak. I would look for a fuel leak, if its enough to make you light headed it should be pretty substantial. The exception would be if you have the tank venting into the cabin somehow so the fumes cant escape.

[KTL]

Last year when I got the racecar I did some refurb work on the carbs too- gasket replacement and cleaning. I noticed one pump had new gaskets/diaphragms on it and I left that one be. Turns out that was where the leak was located. Did a search here on Pelican and come to find its common for the cover plate and intermediate piece to be slightly warped or not have nice flat sealing surfaces.

So I colored the surfaces blue with a Sharpie marker and started wet sanding them on a piece of flat glass. Sure enough the surfaces were VERY uneven. Point of sharing all that is, you might be better off checking the surfaces for flatness instead of simply tightening the nuts. You might actually further the warpage problem by tightening.

Factory lines in the cabin are indeed hard pipe lines. Mine is braided stainless flex hose, so it requires periodic inspection and replacement. I know on my '87 that the rubber flexible unions are outside the cabin, no question about it.

[Grady Clay]

LJ851 brings up a good point.

Use new hose everywhere. The proper hose is available from our host by the meter.

Use the proper Norma-Schellen (N-S) type clamps everywhere.

As maintenance, replace the cork gasket at the fuel level sender.

Take the pan off under the steering rack (4 bolts).
Is your electric fuel pump here or in the engine compartment?
Inspect the fuel hoses and clamps between the gas tank and fuel pipe in the tunnel.
It may be wise to replace these hoses (probably only one) and the clamps.

There is a filter screen in the fuel tank fitting.
You should remove the fitting and clean the screen.

If you want to ‘get carried away’, you can install a circulating fuel system and locate the electric pump and fuel filter on the front suspension cross member.

Search pelican.
There is a lot on this subject.

Best,
Grady

[daniel911T]

Grady,
Thanks a lot for the comprehensive reply!

Sadly, I don't know any of the history of my car before I bought it. Even the body info plate has been lost along the way. The only thing I do have is the VIN, which is the same in the windshield and the trunk. I don't know the original paint color, or anything else. It's sad, I'd love to have that info, but I have trouble justifying purchase of a COA as I know the engine and seats are wrong, and that this will never be a "matching numbers" car.

I have noticed some somewhat strange things about it, such as the lack of hard lines for evaporative emissons, and the lack of a line for fuel return to tank. I realize the carburetted cars did not use the return side, but I'm surprised they didn't install the same plumbing in all the bodies. Perhaps she did begin life somewhere else? I got her in Oregon, so she may have been a Canada spec car?

The lack of return line made install of the PMO regulator a real adventure.

[Grady Clay]

Daniel,

What are the last four digits of your VIN?
There are some very early '69s built while they were still figuring things out.


All these little details can be solved - just one at a time.

Best,
Grady

[daniel911T]

Grady,
VIN= 119121730

[69911e]

My '69 sometimes smells of gas, always has, but nowhere near enough to make you lighheaded. It is just vented outside the car. Mine is not a USA version.
Make sure your hoses are good, the plastic reservoir is not cracked, and the vent does indeed exit the car.

[daniel911T]

I'll be checking all the obvious stuff before I drive it again. I actually started this thread because I wanted to know what kind of tube I should be buying to replace all the vent hoses.

The shopping list now has:
(2) fuel filler neck sleeve, 911-201-515-00-M100
-note, all diagrams show only one sleeve, but my car has two. Both badly cracked and aged.
(1) Fuel tank sender gasket
2 meters, 14mm ID, 17mm OD
2 meters, 9mm ID, 14mm OD

Plan is to go to Grady's super simple system. The car isn't plumbed for a canister, so I'm not going to use it.

Just in case anyone is curious, this is how I worked my PMO regulator into the system with no return lines.




I welcome any suggestions on the shopping list.

-Dan

[RWebb]

I don't think you need hard lines - fuel vapor should be pretty happy with fuel hose (liquid fuel). There is some new fuel hose out with a special liner for EtOH fuel mixes - Goodyear makes it.

venting everything to outside the car is important, but if you have reservoir for fuel (like the one under the LH F fender) then you can get fuel dumping out onto your garage floor; or just a lot of fumes in your garage

this is not safe; if the garage is attached to the house it is even less safe; and even if "safe enuff" will not make you or the popular with people who lack a Y-chromosome -- don't ask me how I know this...

look up under the cowl in front of the driver and see if there is a small back squarish tank there - be sure that and the other reservoir are not cracked in anyway

[m1franck]

Here's some diagrams for '69 & later cars.

Sounds like your car may have had some of these parts removed at some point. There are 2 rubber hose connections inside the cockpit that you may want to check as the source for the fuel smell. Remove the drivers side pedal board and look just forward of the throttle pedal. There should be 2 hard lines that come up from the center tunnel & will have rubber hoses connected to them. These are not fuel lines, but are fuel evap lines that connect to the charcoal canister. These are hoses 20 and 21 in the first diagram.

[daniel911T]

Thanks so much for the detailed drawings!

And this is the crux of my problem.... My car lacks most of that equipment. I don't have the expansion tank (2) I have no plumbing (hard lines) in either the front or the back for the circulation to the engine. I have seen pictures of where all this plumbing should be, and it simply isn't present on my car.

I do have the little black square thingy. I need to check it's soundness.

I would be happy to post pics of the empty spaces where these things are supposed to be.

I will take a closer look at the area behind the gas pedal, but I was just in there and didn't see any tubes or hoses.

It's a mystery. It's either had major changes, or it was just made different.

[jstobo]

For your 69, in the above drawing(for 70-73) you do not have #2 or # 3 or any lines going to the air breather. Grady's first drawing is all you have and as usual he is correct. (I don't think he has ever been wrong although his wife may differ) There are two lines one goes to the filler pipe for venting then the other vents to the atmosphere in the wheel wheel from the expansion tank(#1 abovr). If the small plastic expansion tank(#1) is cracked you will get fuel smell into the cabin. It is mounted under the lip of your trunk on the driver side abouve the fill pipe. You may not even have the tank anymore and the vent lines ar just venting in the trunk.

[daniel911T]

Ok, going to the black box that lives behind the tach....

I know one side is 14mm, and that the other side is smaller. What size tube should I be getting for the smaller size?

Thanks!
Dan

[steve911T]

Daniel, I have a 70T and I had the same problem you did except for one thing, I had all the components shown in the above diagrams connected and not leaking. Do you have the gas smell in the car when it is not running? If so, I would suspect the gas line in the tunnel to be leaking. Can you smell it in the engine compartment when the motor is running or not. If you can smell it strongly in the compartment when running or not running, I would personally not start the car. What I found was wrong on mine was the actual gas tank. When it was full, you could smell gas when the car was moving but not when standing still or been sitting for some time. Finally, I let the tank go almost empty and the smell disappeared. I pulled the tank out and noticed that there were some bubbles on the bottom of the tank which appeared have been generated from inside the tank and yes, they were. Tank bad, rusted from the inside out. Luckily at Hershey last spring, I picked up one for $75 and my tank guy is refurbing it. Good luck. Steve

[Grady Clay]

Here is the 1969 Evaporative Emissions System


© 1969 Dr. Ing. h.c. F. Porsche K.G.
This shows the fuel system for the 911T (pump at rear), #2, 4, 16, 17.
and
the fuel system for MFI 911E & 911S, #3, 4, 7-10, 16-19, 37-42 and more.
(In 1970, the 911T is plumbed as the 911E&S here.)





The ‘tee’ fitting (#44 above) does not show a 3rd connection here.
My recollection is that is the small vent hose to the filler neck.

The outlet goes through a grommet (#47) in the front panel behind the windshield washer reservoir.
It vents between the front bumper and the inner panel.





System for '70-'71.

© 1970 Dr. Ing. h.c. F. Porsche K.G.


Best,
Grady

[daniel911T]

GRADY

Thank you SO much! That's amazing!

This board is absolutely wonderful!

THANKS TO ALL!

I'll let you know how the repair goes.

-Dan