Technical barchetta fuel leak

[tjr]

So on to the next issue....; fuel stank.

Questions:
1) When the tank is full and without any tank pressure build-up, there is a leak around No. 14 (see pic), part No. 46755835. Do you have any suggestions for a solution, eg is there any sense in trying to apply a liquid seal (it needs to hold against tank pressure build-up (and down))?
2) If yes, any recommendations on what product to choose?



Background:
On the one and only longer drive with the barchetta -95, we filled up and drove for 5.5 hrs in pouring rain with the soft top up (oh yes, the soft top leaks like a sieve when standing still (am waiting for new soft top silicone gaskets)), we got dizzy from fuel fumes (and perhaps the noise).

Thanks to this forum I have gotten the fuel tank panel/cover/bulkhead out.

The fuel tank area has a lot of crud in it. I have yet to clean it out, but was keen to look for leaks, so I filled up the tank. The first leak I have located (so far) is around number 14 "Seal gasket" OE 46755835 (see pic). What material is is? I don't yet know if the leak is between the tank and 14 and/or 11 the filler tube. I suspect the filler tube is a replacement part as it looks newer, and has a hose clamp mounted on it at the connection to No. 14. To me if No. 14 is made out of rubber, a hose clamp would make little sense. I have not yet taken the connection apart, but it looks like the filler tube is clamped over the No. 14 seal gasket lip.

On the original mount, how is the connection pressure resistant (between parts 11-14-1)? Is there any description/picture available on how these three parts should be mounted (w/wo clamps and/or sealing compounds)?

Thanks for the read and any feedback!
T

 

[tjr]

Update 1:
I found that the existing clamp was fitted, but not tightened(!).

After emptying the tank from most of its fuel. I disconnected the clamp, and took a (too quick) look at the setup. The fuel tank has a neck upon which the Seal gasket (Sg) (14) is fitted, and on top of that the filler tube (11). The clamp fitted on the filler tube will squeeze it and the gasket around the tank (metal) neck, and should offer a leak-proof solution. I did this with a new (tightened) clamp and tested re-filling the tank.

It leaked worse than before... I (emptied the fuel and) dissembled it all again and checked for cracks, none found. I'm wondering if the Sg has hardened with time, and might be letting the fuel escape. I haven't found the Sg readily available, so I'll try some liquid gasket tomorrow to see if it might seal the leak. On the forum "Permatex Aviation form-a-gasket" was recommended, I'll see what I can source locally.

 

[ernibv]

Update 1:
I found that the existing clamp was fitted, but not tightened(!).

After emptying the tank from most of its fuel. I disconnected the clamp, and took a (too quick) look at the setup. The fuel tank has a neck upon which the Seal gasket (Sg) (14) is fitted, and on top of that the filler tube (11). The clamp fitted on the filler tube will squeeze it and the gasket around the tank (metal) neck, and should offer a leak-proof solution. I did this with a new (tightened) clamp and tested re-filling the tank.

It leaked worse than before... I (emptied the fuel and) dissembled it all again and checked for cracks, none found. I'm wondering if the Sg has hardened with time, and might be letting the fuel escape. I haven't found the Sg readily available, so I'll try some liquid gasket tomorrow to see if it might seal the leak. On the forum "Permatex Aviation form-a-gasket" was recommended, I'll see what I can source locally.

I'm finding a different number for your part. See attachment.
How's your German? https://www.barchetta.club/index.ph...-club-deutschland-e-v-tankmuffen-m1-lieferbar
Maybe some of this helps.

 

[tjr]

I'm finding a different number for your part. See attachment.
How's your German? https://www.barchetta.club/index.ph...-club-deutschland-e-v-tankmuffen-m1-lieferbar
Maybe some of this helps.

Thanks for the response, yes indeed I was looking at the M2-schematics and not the M1... Thanks for catching that.
Excellent find, concerning the German sourcing of the gasket! My German is close to non-existent, but Google Translate is my friend I'll try a new gasket if/when the gasket cement fails (if I can get it off), I applied it Friday, and will be testing today, fingers crossed.

 

[ernibv]

Good luck!

 

[tjr]

Update 2:
So far the new clamp TOGETHER with the gasket cement is holding up to a full tank of fuel.

Next step will be to develop tank pressure through some driving around (plus looking for additional leaks).

The gas/fuel cap gasket will be replaced as it is looking worse for wear, and I tightened the clamps around the hoses attaching to/from the injection assembly. There were some tell tale stains.

 

[tjr]

Update 3:
Just took the little b for a spin with a smile. It is still quite chilly here still, so pressure build-up from hot weather has not yet been experienced, but the fuel sloshing around the tank has not revealed any new leaks. At least for the moment, I consider the fuel leak solved

 

[tjr]

Update 4:
The b has been running around with several full tanks (to the brim), been exposed to a few days with 30°C weather over the past three (almost) months and the above fix has kept the fuel vapours out of the driving compartment. For the moment it's a b without any fuel smell at all, a relief especially on long drives!