fuel tank ventilation - where does this hose go?

[austria3]

Hi all

after replacing my rusty filler neck with a stainless steel version and also replacing the rubber hose between tank and filler neck and replacing the fuel cap seal I discovered a new problem: Last time I opened the fuel cap at the gas station I could hear a loud and long inhaling noise.
Today I took a look under the car and noticed a deformation of my fuel tank:


So I assuemd I have a problem with the ventilation system. I unlugged every hose starting with the one at the fuel tank itself and checked it by blowing trough some compressed air.

The problem is in the last "return" hose from the expansion tank.

One end is connected to the small metal tube (yellow arrow) behind the fuse box and other end is where?

I only can see it here:

But where does it end?

Thanks

[Bob Kontak]

Look at page 113 and 115 of this pdf file. It is the US version so the parts that are on the German / ROW cars are present in the drawing but no part numbers are present. I think you need to focus on parts 20-24 for what you are missing. The numbers change a little bit from the two diagrams.

On US cars it feeds into the charcoal/carbon canister in the engine compartment. From what I can tell, the non-US versions may dump gas vapors into the atmosphere or into the #24 part on page 115. There appears to be two variants.

I have the ROW and German pdf catalogs on my basement computer if you want the part numbers. Let me know what version you have.

http://www.porsche.com/all/media/pdf/originalparts/usa/911_USA_74_77_KATALOG.pdf

[austria3]

thanks Bob for the pdf files

if there are two version this wont get easy:
shell and everything else expect fuel tank, engine, and transmission is a '77 911S US, the other parts are from a '78 SC ROW

where in the engine compartment should I look for the hose?
or is there a metal tube like the standard fuel lines ?

thanks

[Bob Kontak]

If it is a US shell there would have been a charcoal canister that the hose connects to or connected to. That part I believe is in the engine compartment. My US 81 has it on the passenger side inner fender. About ten inches long and oval shaped. Black in color.

The hose starts from the drivers side corner, way back in there, and routes across the rear "firewall" to the passenger side inner fender.

[austria3]

there are actually two metal tubes running through the inner fender. One lager one which goes from the fuel tank to the expansion tank (number 1 on page 113), and one smaller one which is running back from the expansion tank to the aerier behind the fuse box.

taking a closer look to the drawing on page 113 it seems to me like there must be another metal tube between part 28 and 29. Where is this tube and where is the carbon canister exactly located in the engine compartment?

[Bob Kontak]

Yes - the drawing does look like it has some dotted lines indicating something is there between 28 & 29.

I am looking at my car closer - I have a big and little metal tube in the inner fender. The big tube goes to a little plastic box that also receives gas from the over flow tube in the gas filling area. The box is connected to the top of the fuel tank with a hose. I can get a picture if you want

I bet the metal tube is in the tunnel between the seats.

[Bob Kontak]

It's the smaller tube that feeds the canister

[Bob Kontak]

Not sure what an aerier is.

My small metal tube has a hose attached to it and once it goes behind the filler neck I can't tell where it goes but I did find where it comes out. There is a metal tube coming out of the tunnel by the transmission that a hose attaches to. It is on the driver's side. There is a brake line and right above the brake line the clutch cable, then above the clutch cable is the hose from the small metal tube. That is the one that feeds the charcoal canister.

Here is a pic of how the big hose set up is configured. The hose in the lower right of the white plastic box is the hose from the big through-the-fender tube.

[austria3]

Not sure what an aerier is.

typo sorry, meant area

My small metal tube has a hose attached to it and once it goes behind the filler neck I can't tell where it goes but I did find where it comes out. There is a metal tube coming out of the tunnel by the transmission that a hose attaches to. It is on the driver's side. There is a brake line and right above the brake line the clutch cable, then above the clutch cable is the hose from the small metal tube. That is the one that feeds the charcoal canister.

I will take a look under my car and try to find the end of the metal tube

[austria3]

There is a metal tube coming out of the tunnel by the transmission that a hose attaches to. It is on the driver's side. There is a brake line and right above the brake line the clutch cable, then above the clutch cable is the hose from the small metal tube.

here is a picture of the mentioned hose:
hose is indicated by red arrow.

I also found out where the hose enters the metal tube:

right behind the pedal cluster. On the top left it enters the cabin (red arrow), on the bottom right (yellow arrow) it enters the metal tube.

in the engine compartment I located the hose on the left hand side (red arrow), you can still see the bracket for the carbon canister (yellow arrow):


The solution for my problem was to relocate the hose in the luggage compartment. It now runs to the front of the car like it does on the ROW cars:


and there is a screen shot of the PET side Bob and I are talking about:

the red marked parts are the ones I have to buy.

[Bob Kontak]

Stefan - The bottom red part is called an electrical cap - odd name. I will send you the part number. Also if you PM me your e-mail I can send you some useful files.

[hydrocrust]

Originally Posted by Bob Kontak

Not sure what an aerier is.

My small metal tube has a hose attached to it and once it goes behind the filler neck I can't tell where it goes but I did find where it comes out. There is a metal tube coming out of the tunnel by the transmission that a hose attaches to. It is on the driver's side. There is a brake line and right above the brake line the clutch cable, then above the clutch cable is the hose from the small metal tube. That is the one that feeds the charcoal canister.

Here is a pic of how the big hose set up is configured. The hose in the lower right of the white plastic box is the hose from the big through-the-fender tube.

Hi, Folks, Opening old thread.

Can someone tell me what is the name of the white plastic box, two braided hoses coming out at base, one hose in at top? I see it is lots of photos in Bentley, but it is not named as best as I can tell, and I can't find it on the original Porsche parts cartoons. I don't think this is the expansion tank...as that looks more oval on cartoons, but maybe it is aftermarket? I'm pretty much a noobie at this, maybe it is obvious.

Thanks!

[steely]

PET calls it an expansion tank, although this PN may be superseded,
911-201-381-00

[hydrocrust]

Thanks for the quick response, Dan,

I was confused about this because all the photos of expansion tanks I've seen with labels have an oblong shape. I found the same drawing on the parts list, labeled as expansion tank, but I don't think our hosts carry this item, and when I've looked around at other sites, seems like the shape is different. Any reason why I need to use this exact form? It seems like any shape will do as long as I have right connections for hoses, same function, etc.

Best wishes, Andy

[steely]

Sorry Andy, not sure I can answer your question, although I don't see why another form wouldn't work (as long as fuel resistant). I also can't say I've seen the oval version depictions you mentioned either.

Hopefully someone else can chime in.

[wesjs]

Thanks guys I can use this too

[hydrocrust]

Hi, Folks, I've got a 82 SC, had a gassy smell, noted some gas on one of the two braided black hoses attached to one side of the expansion chamber. Inspection revealed that the chamber had been broken and epoxied, had some hairline cracks, so ordered a new one and put it in. A day later, that hose is still a bit moist with gas (although not as wet), not sure if I just need to give the gas time to evaporate, maybe open the hood and let it sit exposed to air.

But I was thinking of replacing one or both of those lines, the two that come off the fuel expansion chamber on one side. One is short, goes to the gas tank, would be easy to swap. I'm not sure about the other one, what it does, where it goes. I can't tell the part number of either for sure. I am looking at the Porsche "Katalog" with diagrams, part numbers, etc. but they don't show anything coming out of the expansion chamber, have to figure it out from other diagrams.

I think that the short one might be the "overflow hose"
901-201-731-00 or 901-201-931-00 (also not sure about difference between these)

Any idea about that longer hose? Might someone know the name of this part and part number? Thanks for your guidance.

[HarryD]

You might find the schematics in this thread helpful:

1973 emision stuff

[hydrocrust]

Thanks, HarryD, that is helpful. I'll bet that second hose goes back to the filler tube. I'll take another look.

[TibetanT]

Stefan:

If you change both hoses on the expansion tank (plastic piece in picture) AND you still smell gas when driving, check your fuel pump hoses as well. I had this very same situation recently where my hose in the trunk (gas tank to expansion chamber) was weeping gasoline. After replacing these, the problem was more prevalent with more fumes entering the cabin.

I found that my fuel smell was coming from a leaking pressure hose running from the fuel pump to the tunnel. I purchased the entire pressure hose from Pelican and now in the process of replacing it (which is a real project).

Good luck and I hope this helps.