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Fuel leak when filling up

 
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chuck21401  



Joined: 20 Feb 2005
Posts: 375
Location: Annapolis, MD

PostPosted: Tue May 11, 2021 1:51 am    Post subject: Fuel leak when filling up Reply with quote

I went to get gas the other night. After adding about 6 gallons I noticed fuel leaking under the car. Looking underneath it appeared to be come from the top of the tank/fuel filler area. I let the fuel evaporate and drove home.

Ran some searches on 924board. Suspects include the hose between the fuel filler and the tank, the vent line and possibly a cracked tank (but hopefully not!).

I opened up the filler neck area. The cloth covered vent line was soaked with fuel; the other lines seemed fine. The larger rubber hose from the filler to the tank was tight and not soaked with fuel.

Returning to the vent line....duct tape. That's not a good sign. I'm guessing there is a crack under there?

From what I've read, the only way to replace the tank vent line is to drop the transaxle and fuel tank. Is that right?

But I don't understand why the vent line would leak upon fill up. Is there enough pressure to push the fuel up the vent line?

Here are some pics. Anything look unusual?




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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1039
Location: Maysville, Colorado

PostPosted: Tue May 11, 2021 2:23 am    Post subject: Reply with quote

Having had a cracked tank. I'd leave the cover off and put more gas in while watching. I don't understand that wet hose as that should be unrelated to a crack in tank. That vent line goes back down and vents in the rear corner. You can loosen the holding straps and drop the tank an inch or two to see what is going on better.

Removing and repairing a tank is such a pain to do, lots of investigation is worth doing first. If has the Audi 5 speed gearbox, it in itself is nasty to get out.
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Rasta Monsta  



Joined: 12 Jul 2006
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Location: PacNW

PostPosted: Tue May 11, 2021 4:12 am    Post subject: Reply with quote

The stampings in the top of the tank may have cracked from years of flexing.

Well documented at Pelican, here:

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/251194-gas-fumes-tank-leaks-read.html
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chuck21401  



Joined: 20 Feb 2005
Posts: 375
Location: Annapolis, MD

PostPosted: Tue May 11, 2021 4:32 am    Post subject: Reply with quote

Thanks for the link on Pelican. Hopefully that is not the problem here.

I pulled off the duct tape. Sure enough the line is weakened exactly where the metal line inside it ends. Below you can see how the line is frayed and most likely cracked underneath. Still not sure how such a volume of fuel would leak out there...the fuel would have to find it's way all the way up the vent line, right?

Will continue to investigate. Will add some fuel from a gas can to see what happens.


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Fifty50Plus  



Joined: 28 Feb 2008
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PostPosted: Tue May 11, 2021 4:34 am    Post subject: Reply with quote

Probably leaked when you filled the tank and the overflow tube and hose got some fuel in it.
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chuck21401  



Joined: 20 Feb 2005
Posts: 375
Location: Annapolis, MD

PostPosted: Tue May 11, 2021 8:33 am    Post subject: Reply with quote

Added more gas to the car from a gas can. I pushed a paper towel down between the tank and the larger filler hose. As I was watching, I could see a small amount gas at the base, circled below. When I pulled up the paper towel it was wet with gas.

I checked the hose clamps on the big hose, they were tight. I thought maybe I could reseat everything and try again. As I loosened the hose clamps to do that I realized that two gaskets shown on the parts diagram on either side of the large filler hose are missing, Part #10 below.

944 201 217 00 is NLA but looks like 944 201 217 01 is available from the usual sources. The large hose is probably due to be replaced after 40 years but appears to be NLA. (Bellows - 477 201 357).





This is part 944 201 217 01
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Last edited by chuck21401 on Tue May 11, 2021 8:36 am; edited 2 times in total
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chuck21401  



Joined: 20 Feb 2005
Posts: 375
Location: Annapolis, MD

PostPosted: Tue May 11, 2021 8:34 am    Post subject: Reply with quote

Fifty50Plus wrote:
Probably leaked when you filled the tank and the overflow tube and hose got some fuel in it.


I'm never that lucky
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chuck21401  



Joined: 20 Feb 2005
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Location: Annapolis, MD

PostPosted: Tue May 11, 2021 8:55 am    Post subject: Reply with quote

MikeJinCO wrote:
If has the Audi 5 speed gearbox, it in itself is nasty to get out.


While the body is a 1981, this car has the engine and G31 transaxle from a 1980 924 turbo. The previous owner installed an intake and crossover pipe from a S2 model, so that made it a lot easier to add the top mounted intercooler.

At some point I'll need to have the transaxle rebuilt. The synchos in 1st and 2nd are shot. From what I understand, switching back to the Audi 5 speed would be no small task. Plus I like the dog leg shift pattern.
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!tom  



Joined: 28 Aug 2006
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PostPosted: Thu May 13, 2021 3:12 pm    Post subject: Reply with quote

I had problems with leaks from my gas tank too. You can read about my saga
here.

Sorry the pictures are gone, but the gist of the story is that the tank would hold a vacuum, but would not hold pressure, due to a failed gasket on the fuel sender. I replaced the gasket and all the issues were resolved.[/url]
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chuck21401  



Joined: 20 Feb 2005
Posts: 375
Location: Annapolis, MD

PostPosted: Fri May 14, 2021 12:27 pm    Post subject: Reply with quote

!tom wrote:
I had problems with leaks from my gas tank too. You can read about my saga
here.

Sorry the pictures are gone, but the gist of the story is that the tank would hold a vacuum, but would not hold pressure, due to a failed gasket on the fuel sender. I replaced the gasket and all the issues were resolved.[/url]


Thanks for the link. I'll check that gasket too.
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