How do I fix this leaky fuel tank?

[Slush]

Hi Pelicaners

A few weeks ago, I had a new gas tank installed. When I topped up the tank, I noticed a strong and unpleasant smell in the cabin. A bit like petrol – or my mother in law. Since I’d never let the latter into my Porsche, I quickly deduced it must be the former.

Almost half a litre had spilled out at what I guess is the fuel return line. I took a photo of it and hope that someone cleverer than me can tell me what I can do about it? Do I need a new tank, or is it simply a matter of replacing the fitting for the return line?

Thanks,

Holger

[82 SC]

Well I would start with the easy one, fitting and fuel line if necessary. Just need to get on in there and figure it out.

[GH85Carrera]

Originally Posted by 82 SC

Well I would start with the easy one, fitting and fuel line if necessary. Just need to get on in there and figure it out.

I try and not be a smart ass and reply "don't put gas in that tank" and it will not leak gas, but I just can't resist.

I have to agree with the post above, check the line and the clamp. It is easy to have a small tear in a hose or a clamp that is not tight enough. It will be a stinky messy job.

Worst case, drain all the gas, remove the tank and pressure test it.

Good luck.

[ossiblue]

Since the tank is new, it's unlikely the metal tube connected to the tank is bad, although that is not impossible. More likely, the rubber hose itself is cracked and the fuel is leaking through the rubber and woven covering. Looking at your photo, the clamp on the hose looks to be factory type which cannot be removed without distortion or unless the grip on the metal spout is weak. Further, the hose is sharply curved where the fuel is leaking--another typical cause of fuel leaks through old, cracked hoses. This curve is where the metal spout meets the interior of the hose thus further causing the interior lining to be cut.

Replace the hose from the tank to fuel pump, install new clamps and, IMO, your problem will be solved.

[3.0schotrod]

Your picture loks to be looking under the fender, drivers side ? is that correct

If it is, that looks like the fuel breather hose that comes from the Y piece under the trunk between the breather point on top of the tank to the fuel filler neck

The tube you see is the one that goes to the fuel breather tank under the fender, if im right.

For fuel to be coming out of there, and having just replaced all my hoses, and tank, and re routing the charcoal canister, you would maybe have afew things going on.

Could happen if the tank is completely full and the breather system is blocked somewhere. One way to check is to leave the car in the sun for a while in the heat, then crack the fuel filler, on mine I got a lot of pressure release showing the breather system was blocked and pressure was building up.

If this is the case I would run some fuel off, and first check the rubber pipe fitted to that metal barb you see on the picture.

It could be that fuel is syphoning into the fuel tank breather canister under the fender.

If you find concerns, I can tell you how the breather system works, it looks complicated, but its easier than it looks.

[Discseven]

Originally Posted by Slush

Holger... is there a small crush clamp on the hose?

[Slush]

Originally Posted by 3.0schotrod

Your picture loks to be looking under the fender, drivers side ? is that correct

If it is, that looks like the fuel breather hose that comes from the Y piece under the trunk between the breather point on top of the tank to the fuel filler neck

The tube you see is the one that goes to the fuel breather tank under the fender, if im right.

For fuel to be coming out of there, and having just replaced all my hoses, and tank, and re routing the charcoal canister, you would maybe have afew things going on.

Could happen if the tank is completely full and the breather system is blocked somewhere. One way to check is to leave the car in the sun for a while in the heat, then crack the fuel filler, on mine I got a lot of pressure release showing the breather system was blocked and pressure was building up.

If this is the case I would run some fuel off, and first check the rubber pipe fitted to that metal barb you see on the picture.

It could be that fuel is syphoning into the fuel tank breather canister under the fender.

If you find concerns, I can tell you how the breather system works, it looks complicated, but its easier than it looks.

Hi

Thanks! Yeah, the picture is from under the fender on the driver's side. The fuel spills out when I top up the tank or after some rigorous track day driving. I spoke with the guy who installed the tank, and he thinks it might be the breather system as well. He gave me a few instructions and it seems like a pretty easy job, so I will try that first.

cheers/holger

[Slush]

Originally Posted by Discseven

Holger... is there a small crush clamp on the hose?

Nope, there shouldn't be one.

rgds/holger

[HarryD]

That is part of your evaporative emissions control system. The hose collects fumes into the tank in the wheel well. In my car, I have noticed that sometimes when I fill the tank this line will have fuel in it. Also, if I Autocross with more than a half a tank. The line fills. You may need to Replace the hose or tighten the clamp. Here is a drawing of the system. If you search for "evaporative emissions" and look for posts by Grady Clay, you will get all kinds of information.

Originally Posted by C4 Pazzo

Thanks for the responses. Of course, my car is not an MFI. I wonder if the fitting is meant for a later type of emissions vapor recovery. The car had A/C retrofitted and the intake is oriented to the left instead of the right to make room (for the since removed) compressor. Perhaps the air filter box is from a newer car.

Looking at the ventilation diagrams reminded me of another vapor system question. When I cleaned out the vapor lines with compressed air, the line that I thought was coming from the fan into the charcoal filter spewed out foamy gunk that looked like the frothy oil/water mixture one sometimes sees. I was surprised to see it in that line, but now I wonder if I might have my inputs and outputs mixed up, since it seems more probable that oil might have gotten into the other line since it is connected opposite the oil breather hose.

I took a look at the two diagrams below from the thread Grady linked and noticed that for the early cars the line into the charcoal filter is connected at the side of the filter with two connections, whereas for the '74-'78 cars the input line is connected to the side of the filter with the single connection. I was relying on my Haynes manual and now wonder if the diagram shown was for a later car. It seems a little odd that the input and output connections would have changed unless the charcoal filter design changed (or maybe the direction of flow doesn't really matter), but I think I better go with Grady's early diagram as the guide and reconnect the hoses.

[Slush]

Thank you very much! That's really helpful.

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