Gas smell in boot - trying to pinpoint the issue

Dear all,

I am the proud owner of an ‘82 XJ6 series III. I love the car, but unfortunately have a gas smell in the car and definitely while driving with the windows down (causing headaches). I extensively read through various forums, but nonetheless wanted to ask the communities’ advice. This is my first post, so bear with me. Happy to join the jaguar family!

Driving with the windows down generates an under-pressure due to which the gas fumes of the boot get drawn in. I tried to fix the vent flaps (‘cowbell phenomenon’), so the fumes shouldn’t be drawn into the cabin too much anymore.

However, issue remains that there is a serious gas smell in the boot. I used a gas detector to pinpoint any leakages / location of the fumes, while the car was turned on (engine running) and in Neutral. This is what I have found:

  • heavy gas smell coming out of the fuel turnover switch and or the hoses attached to it (2500+ ppm)
  • very heavy gas smell coming out of the hole of the internal bodywork via which the hose/pipe coming from the fuel turnover switch goes to the left tank (5700+ ppm) - I think the rubber that should close off the hole has some openings in it. But nevertheless, is it normal to have such a gas smell coming from there?
  • heavy gas smell coming out of the same hole on the other side, going to the right tank (3100+ ppm). Similar story.

I’m wondering what the issue could be here. There are some candidates like e.g. a leaking tank but before I dive into that, maybe the collective wisdom of the community can tie the 3 measurements together to one specific issue/phenomenon?

I’ve added a picture to clearify the specific locations in the boot.

Thanks in advance!


Hi Stefan,

I had the same problem with my 86 Series III. There was a constant petrol (gas) smell generally around the back of the car and in the boot (trunk) and with the windows open while on the move I got a strong smell in the car.

After checking that there were no leaks in the engine compartment, checking all the hose connections in the boot and checking for leaks from the tanks, I came to the same conclusion that it was probably swirling up from the general area of the petrol tanks and being sucked into the car. I also checked that the vent holes in the filler necks were clear and all vent hoses were secure. Fortunately, my car has air conditioning so I don’t have the windows open too often and I lived with it for some time.

Anyway, one time after swapping between tanks I could hear the pump struggling and noticed I was leaving a trail of fuel behind me. It was running out from somewhere around the middle of the back axle! After investigating I found a pipe that appears to run from the vapor traps in the C pillars and exits behind the center of the axle. I can’t find any mention of this vent pipe in any of the manuals and parts books I have so it may be a late modification?

It turned out that I had a lot of rust in the tanks and pipes causing a blockage and it seems somehow fuel was being pumped up through the vapor traps and exiting via this vent pipe (at least I couldn’t find any other connection to it). The C pillar traps also still vent back to the petrol tanks as normal.

I fitted one of the small see through fuel filters to that vent pipe, only the reverse way round, to see if it would make a difference. The smell in the car with the windows open hasn’t gone completely but it is much improved. It has also been suggested to replace all the fuel hoses with modern low gas permeable ones, which I haven’t got round to yet. That may help improve things too.

Hope that’s of some help.

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Hi Stefan and welcome.

Start with the easy things first, change ALL these 30 years old hoses, including the vapour recovery ones on the C pillars.
It sure looks like they are leaking at the joints, they are hard and tired…
Something like Low permeation Gates Barricade hoses is highly recommended.


Thank you for the replies already!
Ray, I didn’t know about the vent you mentioned, will definitely look into that. Anyone else aware of this?
Aristides: your suggestion is definitely necessary, these are some old hoses, etc.

Regarding the fact that I can detect gas at these 3 spots at the same time, could that point to any potential specific issue?

[quote=“XJRay, post:2, topic:430893, full:true”]
…noticed I was leaving a trail of fuel behind me. It was running out from somewhere around the middle of the back axle! After investigating I found a pipe that appears to run from the vapor traps in the C pillars and exits behind the center of the axle. I can’t find any mention of this vent pipe in any of the manuals and parts books I have so it may be a late modification?

The fuel separators in the C-pillars each have three hoses, Ray; one from the filler lid, one return to the ‘bottom’ of the tank - and one to the charcoal canister conjoined left and right ‘somewhere’. There should be no liquid fuel in the hoses unless a tank is overflowing - usually due to a fuel return valve malfunction…

However, the single fuel return line from the pressure regulator, always containing fuel, is split into two hoses to the ‘left’ and ‘right’ by a difficult to access ‘T’ above the rear axle…

Not that it necessarily applies to Stefan’s problem, but is for your attention…

The Jaguar is, as you imply, designed to run with the windows closed. Open windows may draw fumes from any source into the cabin. But fumes indicates a fuel ‘leak’ somewhere requiring some attention. Except that the ‘European’ set-up legitimately vents tanks to the open air…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

For fuel hoses in the boot I’ve had great luck with Marine grade fuel hose, SAE J1527 A1-10 and A1-15.

It is very thick walled, ultra low permeation. IMO, much more effective for the confines of the boot than automotive grade hose


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Way back, former lister, alex Carnara addresses the smely boot issue. Ther is a boot vent to tje atmosphere. he added a small fan. taken from a defunct computer powered off te fuel pump circuit.

i salvaged a similar fan and planned to install it. One of tose never got to it projects
There are vent under the rear valence. i fpund mine squashed closed. A pry bat opened them and doid not dmage the paint.


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welcome aboard!

Nauseating fuel smells almost inevitably are caused by leaks. Gasoline permeating through hoses will cause that whiff and make your luggage smelly, but not make you sick in the cabin.

So, I’d first remove all covers, cover fuel pump, hoses, t-valve etc. in talcum and then try out the car with left and right tank in movement, at speed etc. to check whether you can spot a leak. Without talcum it is hard to see as fuel quickly evaporizes.

Then continue with the tanks. Get yourself a cheap USB endoscope for your smartphone or laptop and peek into the empty (!) tanks. Be very careful as empty tanks contain most highly explosive gases … Pinholes in the tanks may cause that kind of problems, but usually only occur on pretty rusty tanks.

My car had a leak on the metal fuel pipe leading from the tank compartment into the silencer box. The rubber grommet had deteriorated. Then the metal pipe had vibrated against the body sheet metall and eventuall developed a hole. I was able to cut the pipe and refit the rubber hose.

Finally, on a federal car check out the fuel fume evaporation system as described. With the analysis you already made you might turn directly to steps 1 and 3, replace the hoses, check out the vapour recovery system and hope you got it right!

Good luck


75 XJ6L 4.2 auto (UK spec)

Talcum, what a great advice!!

@Jochen_Glockner, what do you mean by the ‘silencer box’?

I have a European car btw.




not sure wether “talcum” ist the correct term in English … that is what I mean: I usually put it on my rubber door seals before winter … and you don’t buy these quantities;-)

The tanks are located outside the main body structure in the rear wings. Looking at the car from underneath you’ll notice that there are box-like recesses in the under-body structure that house the rear silencers.

The fuel lines have to be led through these boxes before they enter the trunk section.

This picture was taken before the rusty metal fuel line was shortened. The fuel lines are crossing these silencer boxes and, of course, need to be routed above the silencers.

Good luck


75 XJ6L 4.2 auto (UK spec)

Probably, but right it is not :grin:

This is exactly (!) where the fuel smell comes from, in your last picture, where the fuel lines from the boot enter the body structure. There is a sort of rubber surrounding the fuel line that should close off that hole in the bodywork, but it has cracks in it. So the gas fumes come in through those cracks.

However - if I’m interpreting it correctly - the cause for the fumes may be a leaking tank but equally well the issue you had.

PS: I understood the term talcum correctly :wink:

The grommet alone should not cause petrol smells. Obviously. Get under the car and see if the line is wet. It is hidden, perhaps by an asbestos shield, just aft of the exhaust silencer. The pipe passes underneath the exhaust into the boot and may leak, or the joint to the tank may leak.

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By the way: you mentioned you ‘shortened’ the fuel line. If you cut a part off, there is not much fuel line left in the boot. So I guess you then pulled a new fuel hose through the hole instead of the fuel line?

The asbestos shield… sounds a bit frightening. I guess you need to be extremely careful while working on it.

Asbestos is perfectly harmless unless you work in an asbestos mine or processing factory, or handle it every other day. Asbestos is very unhealthy in high concentrations but once a year will not cause you any harm. Not unlike spray paint, a few times is fine but you really need protection if you expose yourself often. So don’t worry, it’s harmless to us.

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I’m trying to find the post where this idea is explained. I know it just works on the symptoms rather than the cause, but the idea of that fan is interesting nonetheless. Can you trace the original post back where this idea is explained? Trying to see how it was installed precisely.

I believe there’s two versions of the computer fan. Cannara put one into the boot „drain“ and had it push out the air. Another option was a fan in the cowbell compartment that pushed cabin air into the boot.
I think you should be able to find something by adding @Cannara to your searches.


as David noted - the problem is not the less-than-airtight rubber grommet, but a serious fuel leak in the fuel line behind.

In my case the metal fuel line was rusted through pretty much where you see the rusty spot shortly after the deteriorated rubber grommet. We undid the fuel hose (only with an absolutely dry tank or you will not be happy!), were able to pull it out slightly (maybe 1-2 cm) and then cut it with a Dremel behind the rust spot. Of course, we had to replace the rubber fuel line in the trunk with a longer bit, and mounting the clamp half-way behind the hole was tricky as well.

To clarify for a SII car:

We’re talking the metal fuel line C.30415.
Certainly it would be wise to replace the rubber grommets if you intend to replace the hoses anyhow. If you replace the hoses you’ll also have the chance to check the state of the metal fuel tubes.

Unfortunately, anything behind the opening in your trunk is very hard to be replaced. Basically, you need to remove the silencers and/or the rear bumper and the quarter panel to get access to the metal lines running from the tank toward the trunk. To save Jaguar, the lines behind the quarter panels lead a very protected life and typically still look good well after 40 years. My problem was rather mechanically inclined and probably caused, when the PO replaced the tank (as per the pic in post #10).

I don’t know whether you’ll get away with the hoses or have to do the tanks, but it is comparatively easy to start with the hoses in two shifts (left and right once the tanks are empty) and see how far you get … if it is the tanks you haven’t done any harm and everything you did remains useful.

If you get that far, btw, the heat shields may contain asbestos and, no, even though my life expectancy is already considerably shorter than David’s, I would not be as generous as he is. Stil, asbestos is no problem as long as it remains unfettered. If you decide to remove the shields (they are mounted with plastic fasteners and/or rivets, IIRC), spray them with water. The cancerogeneous stuff is asbestos fibres that are set free when working on asbestos, esp. sanding, drilling or sawing asbestos material.

Good luck - with the fuel issue!


75 XJ6L 4.2 auto (UK spec).

Wow, a blast from the past! A small 12V fan exhausting out boot floor
vent and connected between the fuel pump wire (+) and body does the job…

All Electronics in LA may have the fan.

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