No saving these fuel tanks

Right hand tank coming out, looks okay from this angle - but the entire bottom has a fiberglass patch from a years ago rust repair.

Yes sir that is decades worth of sediment and rust you are looking at on the bottom drain out. Plus you can now see the fiberglass patch.

Oh dear, yes that is the fuel tank strainer removed and sitting on the ground - caked with muck, yuck!

This is the clogged fuel tank outlet, this connects to the fitting/feed line that goes into the wheel well area.

No need to test this fuel tank level sending unit - it is rusted in position!

It was hard to get a good shot inside the tank, but I can assure you that some of it looks uglier than this!

Technically it is true that anything can be saved - but for me it will be new tanks sending units hoses etc.

Probably there have been older XJ’s scrapped out over the cost of this repair for owners who do not do the work themselves and have to pay shop rates. Its not especially bad in comparison to other intricate repairs I have done - but it is tedious with many hours of labor.

You can use the more common Series III fuel tanks that might be easier to find.
Motorcars LTD (British Parts International) in Houston used to have fuel tanks for sale.

A few modifications will be required to fit the later fuel injection style tanks but they will work.

Hello from about 250 miles East of you.


Thanks for that tip Bob, I’ll keep that in mind if I don’t like the new replacement tanks made by Spectra.

Oh, Lord!
You know you’re forcing me to do the same thing, and I’m not looking forward to it. Ignorance is truly bliss :wink:

I 've just been caring around fuel filters in the boot. swap them out about every month when they start to change color. Crap, I’m gonna have to pull the tanks. Ugh!

The old tanks certainly are pas it, Thomas…

xj6 85 Sov Europe (UK/NZ)

I’ve seen and cleaned u some “!@$@#@$%$%#@#” tanks, but nothing like those.

On the + side, the decision is easy. Costly in $ and energy, but easy.

I tried to make a fuel tank of fiber glass It was a glop. More than likely a good thing. Nobody got hurt it flunked the leak test big time.

That’s the thing about "Barn Find’ cars: the paint can be buffed and brought back to life like I have done here, but after 23 years of sitting in that man’s garage some of the inner bits have decayed in archeological fashion.

Mark, I’ll be happy if I inspire you or any others to dig in and do the work that needs to be done. Wouldn’t it be nice if there was a show a hundred miles or more away and you once again had a longer distance capable car to make a day of it? I’ll make the suggestion that you make it a lazy repair process in which you don’t try to do everything in one day. I’ll even be happy to give you a more long winded explanation of all the details I have omitted. You can do it!

Carl, with all the changes that pump gasoline has undergone, I wish that stainless steel or polypropylene replacements were available. Otherwise fast forward a few decades into the future and even the current ni terne steel aftermarket tank replacements will have become rusty.

After a little online research - the ideal material is HDPE - high density Polyethylene. This can be injection molded or with a mold where they drop in some bilk material, and the mold is closed up, and rotates on a gymbal system while it is heated. I saw one of these at Raven Industries in Sioux Falls, SD. They were making VERY large storage tanks - like 10 feet or more across.Something like the XJ6 tanks COULD be made by one of the prototyping firms around the US, - my guess is between $5,000 and $10000 to prototype it. But then there is the liability if you decided to sell them. We’re talking about an automobile component here, full of gasoline! Would be nice to plastic replacement that didn’t rust.

Wouldn’t it be more practical to just fab tanks out of aluminum? There are lots of shops that make fuel tanks for marine applications out of aluminum. Seems to me you just take them the old tanks and say “Fab me replacements” and they weld together something that’ll never rust.

Probably aluminum or steel. I’m seriously considering drawing up a plan to remove the XJ6 wing tanks and fabricate a single tank that would go in the boot space in front of the spare. It would have somewhat less capacity, but be a little safer than those wing tanks which would get crushed in a fender impact. I could attach Both filler holes on the fenders so the car could be gassed up from either side to fill the single tank. Put a drain in the middle, and move the fuel pump to the front of the boot.

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Not a bad plan, but I think you will have a very small tank and very limited autonomy.
If I was to go on all that trouble and expense I would either remove the spare and use all that space, or move the ECU and put it behind the rear seat.

Considering that reports on such crushings are few and far between, Gil, and fewer causing any disasters - it’s hardly worth the inconvenience?

Admittedly, Jaguar was forced(?) to move the placing of a single tank to your proposed position in the xj40, but actually retained the capacity.

xj6 85 Sov Europe (UK/NZ)

I opened the boot last night and took a quick look. There appears to be room for moving the spare down. That would place the tank and accessories (pump, filter, piping towards the top with the spare at te bottom. I’m pausing this project for now to give me a chance to examine the tanks and their condition. If it becomes necessary to replace them, (or even remove to fix) I’ll seriously consider the single tank option. It would make a nice conversation starter - being able to fill the car from either side.

Decades ago. CA mandated old steel under ground gasoline tanks be tested for leakage. many, if not most failed. Removal mandatory.
A major chemical company designed and marketed fibreglass units as non corrosive. Ugh, they split at the joint!!!

At one time, i tried to make a fuel tank from resin and mat for my Austin dune buggy/ looked awful and leaked like a sieve. Two WWII Jerry cans were far better…

24 gallons is a lot of fuel. even for a thirsty Jaguar…

Does not the XJ40, using a similar body use a single tank. In lie of the ECU. light detector and other stuff. Just behind the rear seat.


I’d suspect that the twin wing tanks were Jaguar’s response to the consequences of the design decision in favor of that tapered rear end and the voluminous IRS. At the time fuel tanks were mostly placed behind the rear axle underneath the trunk. Not enough height available. It may have appeared clever to use the hard to access space inside the wings for the tanks. And no, I can’t see any particular risk in case of accidents. Jaguar XJs are loved by banger racers. I’ve never heard of any incident related to the location of the tanks.

The later position between the cabin and the trunk makes it hard to use the wing space and/or requires a different layout of the rear end. The XJ40 abandoned the IRS with inboard brakes and had a higher trunk line.

Most modern cars have plastic tanks molded into the shape of the car body, underneath the rear seats etc. Thank you, Carl, for your report! I would have loved to replace the XJ wing tanks by modern plastic parts - but this is certainly not a DIY job!

Good luck


75 XJ6L 4.2 auto (UK spec)

One of our club members had a Broadspeed replica and that has a ‘40 tank in the boot.

Hi Jochen,

It started long before the IRS with the MKVII in 1950. I think the motivation was a bigger trunk. I have a MKV DHC, single tank under the boot floor, very strangely shaped and small trunk, almost as bad as an E-type OTS. :slight_smile:


The twin tanks were designed both for the two spaces that were available but also to give the car better handling and balance. Imagine 20 gals (180lb?) sloshing from side to side in a conventional single tank. Definitely the twin tanks give the XJ6/12 Series I to III better poise and it’s great to have a second tank if something goes wrong with one of them.

You’re supposed to fill one with regular gasoline and the other with rocket fuel, are you not?

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