924Board.org

[v8carreragts]

My first 924 did the same thing. (gas smell when full) On mine it turned out to be the plug on the top of the tank leaking. Looking at your pictures it looks like there is some rust and the paint is pealing there as well.

My 944 had two cracks that I patched but the top of the tank is a little different than the early 924 tank.


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84 944--924 Carrera GTS clone w/520HP Chevy 302 V8--RUNNING!
2015 AUDI Q7
2013 Dodge Charger R/T AWD HEMI
2013 Chevy Cruze

[!tom]

[!tom]

Clearly replacing the fuel sender O-ring solved all leaks that I had, because now when I take the gas cap off, there's a big woosh of air out of the tank. On occasion, its been so strong that it has nearly sent the gas cap flying out of my hand!

On the occasions where there is a really big woosh of pressure being released, I hear a sound coming from the gas tank as it relaxes to its proper size.

Now, I do have flexing of the gas tank every time I gas up, whereas previously there were enough leaks where it would never flex.

Does this mean that one-way valve should be replaced with something else?
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78 924 NA
5-lug

[larchie]

Definitely the one-way valve or the bleeder value should be checked.

Generally speaking, the "whoosh" would be greater as the temperature increases the the amount of fuel decreases. It's quite possible the fuel ventilation valve or bleeder valve (cf., 2A in 1976-79 924 diagram below) is stuck or installed backwards.



The loud "whoosh" is common in 924s and 944s, but it should be corrected.

[!tom]

That 2a in the diagram appeared to me to be a one-way valve, and I was pretty confident I installed it in the same orientation it was in when I took it off.

I don't recall which way that was, but given the behaviour, it sure seems like it's installed to allow air in the tank to replace the fuel that is drawn out, but does not allow air out to account for thermal expansion of the air.

How is the system supposed to be configured?
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78 924 NA
5-lug

[larchie]

Actually, as I understand it, the fuel ventilation valve's function is not specifically as a "one-way valve" (which I should have pointed out in an earlier post in this thread) since it acts as a kind-of two way valve depending upon initial conditions: (1) when the pressure in the tank is too high the vapor is vented to the charcoal canister., and (2) as the fuel leaves the tank, the ensuing vacuum can draw air back into the tank. So just to clarify a bit, a little "whoosh" is normal on occasion when removing the cap.

There's an excellent discussion with outstanding images and diagnostic tips on page 3 of this thread of the Pelican Forum Gas fumes? Tank leaks? Read this.

[Paul]

Some non environmentalists just leave the cap slightly loose....
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Rasta Monsta]

Another guy on Pelican replaced the Porsche piece with a piece from another car and successfully reduced pressure build up.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[!tom]

Yah, but that was a 944 setup, which is different in ways I'm not familiar with. His discussion (which I've linked to in the first page of this thread, unless you're referring to a different one) discussed a roll-over valve in the same context, which I don't seem to have.

If it's as simple as described even though the system is different, then that's great. Given that the systems are different, I wasn't sure if the advice was good (as seen in my comments on the previous page).
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78 924 NA
5-lug