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Updated: Fuel vapour smell from fuel tank area

MJL944

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Howdy Gents & Happy New Year to all,

The S2 & I took only our second journey together this morning, a wonderful 30 mile blast along deserted dual carriageways to the south east of Nottingham. Why can't driving always be so pleasant?
The car performed impeccably.

She let herself down a little when we got home though. She deposited just a few drops of coolant at the front which I'll get sorted. It's what was being deposited at the rear that got me more concerned.

When towelling dry the rear arches I noticed the distinct whiff of petrol vapour around the fuel tank area - not a huge whiff but it was certainly there.

I grabbed a torch and after peering into the whole of that area I'm certain there's no major petrol leak there & there's no drips on the floor. The smell was certainly strongest coming from the area of the bottom of the fuel tank. The vapour wasn't coming from the filler cap area (I'd put a third of a tank in at the start of the journey) or inside the rear arch.

The vapour smell was completely gone after 30 minutes and when I checked 4 hours later there was no vapour smell or drops on the floor.

I've searched the forum & I'm aware things like the filler pipe joint clamps & the fuel filter can leak fuel but the smell did seem to be localised around the bottom of the fuel tank.

Is it possible that a (soon to be) 24 year old plastic fuel tank could just be oozing a bit of vapour - maybe along an internal seal or suchlike? Or is that unlikely and there'll definitely be a leak somewhere?

She is going to see the local specialist very soon but I'd just like to hear of other owner's similar experiences.
(BTW - service history reveals rear fuel lines were completely changed in 2002 when the car failed an MOT on a rear fuel leak so the lines aren't original)

She is nearly 24, so she's bound to be a bit incontinent!

Thanks in advance.
 
Slight leak on the fuel filter or a corroded leaky pipe that connects to it? it's proximty is close to the tank on the same side.
 
Thanks Scott, I suspect you're right but I'm crossing fingers it's the fuel filter seal and not a corroded pipe. Has literally just passed an MOT but she's been little used for the past 4 years and the kind of joyful blast she got today will probably throw up an issue or two with seals that haven't been asked to do much recently. I'll update on the issue when Adrian at AMB in Nottm has a look in the near future.
 
I'm not sure if this is a 944 issue or not but assuming there's an O-ring or gasket under the fuel tank sender unit, it could be that it needs replacing?
 
It might be something easy and cheap to replace, such as a short pipe around the fuel filter, but unfortunately it will probably the fuel lines which are starting to become porous. Every car is going to need its brake and fuel lines doing at some point. Depending where you go and how you do it, it can be very expensive or surprisingly less than you expected. Simon
 
This could very well be cracked vent hose. There is a vent hose alongside the filler pipe which is known to crack after time. It would "act up" after adding fuel - especially if you fill it... The filler pipe seems to be sturdier than the vent but apparently still susceptible to shrinking causing loose clamps, etc.
 
The metal clip that holds the hose between the pump and tank can rot, have seen this before. Also not unknown for the clamp to be loose. Have a good sniff aorund the large metal cover at the base of the tank. Also the pressure side can leak where the hose clamps on to the end of the pump. Worth dropping the strap off the tank and having a look. An easy job to do after the offside wheel has been removed, Alasdair
 
Like the other comments most likely to be fuel lines starting to corrode, i was told by my MOT place fuel lines are not an MOT failure unless petrol is visibly leaking then only an advisory strange I know. My S2 does smell a little of petrol when it has first been filled up but only when it has a full tank and that I put down to the fumes from the vent.
 
Hi, About 10 years ago the fuel lines sprung a leak on my 86 turbo. It was caused by corrosion. On the recommendation of my local specialist the complete fuel line was replaced with nylon, using brass couplings. The cost was £180. I've never had any trouble since. You may wish to consider this as a lower cost alternative to replacing the steel pipes. Nylon is the same material as your fuel tank, and many modern cars use the material for the lines too. Regards
 
I similarly had my fuel lilnes replaced completely using lines and fittings normally supplied to GM from what I can see Nylon or similar solvent resistant material that was over three years ago and no problems either with solvent or mechanical issues. Think my local garage did it for around £170 including materials.
 
UPDATE: Thanks for the useful replies & suggestions to my original post. This fuel vapour problem is being looked at now by my local Porsche Indy who can find no evidence of a fuel leak. His suspicion is, therefore, that the breather/vent hose that runs parallel to the fuel filler pipe at the top of the fuel tank has cracked/spilt, as per Bruce's suggestion above. Neither of us want to go through the trauma of dropping the fuel tank so my question now is, would it be OK to 'live with' the issue for a while (a year or so)? I have tentative plans for a transaxle refurb next winter so I'd like to wait for that job which would enable a tank drop so I could replace everything up there then. What do you think? Or, is it too risky and therefore something I should get fixed immediately? The car is not a daily driver & I'm limited to 3k miles a year. Obviously, if fumes started entering the car I'd get it sorted pronto. Thanks for any advise.
 
I had this recently on my 968 Cab, turned out to be the the fuel sender unit rubber seal, we could smell it inside more so when stationary, it was a cheap fix worth doing just to eliminate that one! Fuel smells well covered on 968 forum thread runs over a couple of years! Fuel pipes can be an issue but only detected if put on a ramp with engine running as it's a pressurised system! Another easy fix cause is the seal around the filler cap which can leak fumes as under pressure when running and for a time after engine stopped! Good luck & hope it's simple as the possible causes can be many & varied as I found out at the time!!
 

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