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Spitfire Mk 3 New Fuel Tank ... long story


eddyinfreehold
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I've had this car for about 3 years now and have been slowly ironing out the mechanical faults in it. The bodywork and chassis are superb for its age. I posted last year about rebuilding the carburettors and there was some discussion with very helpful advice on throttle return spring location. I've solved various front caliper issues but generally all has been good.

New story. Once it was appropriate in our covid19 world to feel safe taking the Spitfire out for a run in May, I decided to fill the tank to the top for the first time and have a long run, perhaps 150 miles plus. Having travelled 1 mile to the local forecourt and filled up, went to pay, came out and found fuel pi55ing out of the boot onto the floor. Panic. Removed spare wheel. Removed rear boot card. Petrol leaking from a pin hole on what was clearly a tank patch. Stuck my thumb over it and was able to stop the flow. Felt like the Dutch boy in the Dyke stopping the sea coming in. People come and go and stare, some took photographs of the car !!!  until a contractor from Warrington pulled up in a Transit pickup. We had a discussion and to cut a long story short he went back into town and came back an hour later with a roll of gaffer tape. When most shops were covid shut! It solved the problem immediately with enough tape. Never got the guys name and he wouldn't take any money. Total hero. there are still good guys about. My thanks to the gaffer tape man from Warrington whoever he may be.

Anyway. First step was I siphoned the tank to near empty. Four gallons into cans I think. About another gallon lost on the forecourt over two hours. Did a lot of reading about tank repair .v. replacement and decided upon a Rimmer non OEM steel tank. The SAFE OPTION. That arrived about a month ago as the full kit including new sender, seals, bolts, washers etc no problem. Set to yesterday, first opportunity. Removal of the original tank was straightforward though it required sockets with extension rods, spanners cannot do it. Installed the new tank and then the problems started. The securing bolt holes from the non-Oem unit were poorly aligned but I managed to secure 4 out of 5 after 2 hours sweating. The rule is secure the bottom ones first and only just thread each one sufficiently for it to stay in place, then tighten up as if you were torquing a head so as not to strip threads. Tank in place. Filler tube is now too long and prevents filler cap assembly from fitting flush to the rear bulkhead body in front of the boot, it protrudes by some 3/4" because metal touches metal and there is also a slight misalignment but the short hose can be connected. I can't resolve this at the moment but decided to leave the filler cap proud by 3/4". On reconnecting the fuel pipe and tightening it up I thought we were on a roll. Not a bit of it. I poured half a gallon in and it started dripping straight out of the pipe connection. I didn't want to strip anything but as tight as was reasonable it would not seal. Rethink.

Took a plumbers pipe cutter and removed about 4" of pipe on the L bend including the sealing nut and the well fixed olive. Off to the motor factors who ummed and ahhed but couldn't help, but suggested I try an hydraulic engineer. Looked up several and on the 4th attempt on our local industrial estate found an enthusiast who was interested. He provided me with an hydraulic connection elbow, a JIC 37 degrees ??,  that threads into the new tank perfectly with a solid seal. The elbow can be rotated to the appropriate angle to align with the cut off metal fuel pipe then similarly tighened up to seal. The union between the original fuel pipe and the new hydraulic elbow is made with 5mm i/d modern ethanol proof fuel pipe and appropriate hose clips. Refilled with 1 gallon of fuel. Waited for an hour. No leaks. 2nd gallon. One hour. No leaks. 3rd Gallon. No leaks. The next stage if its all sound is to take it to the filling station and fill to the top to check the sender seal. A 45 min 10 mile run tonight with 3 gallons slopping around showed no spillage.

Worth noting that the old tank had a replacement sender identical to mine and the rubber washer on the float was missing and the float was chock full of petrol, explaining why the gauge never registered. Poor quality. Not expecting wonders. Might remove it later and put a more reliable float on.

Looking at the old tank I'm very tempted to repurpose it as a smoker/barbeque if I weld some rebar legs on and cut the seam in half.

 

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The bottom union can be a pain. Mine took ages to get it to seal, because the fittings currently sold for it have too much unthreaded on the tip for the shallow thread in the original tank. The new tank I bought from Paddocks has a deeper thread, though the hole beyond it feels too fat for the pipe (but too small for the next size up) so I'm not yet convinced the olive will seal properly when I fit it. I may need to get hold of one of those JIC fittings myself.

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9 hours ago, Pete Lewis said:

good to see you got there in the end  , ive seen a local spit empty the tank from a dodge bottom supply union 

removes underseal and floods the garage , a right mess

Pete

If you look at the paintwork below the new tank you can see the light red respray paint that peeled off, the original darker red as delivered and the yellow protective undercoat from 1969. Plus as you say, the sealant between rear bulkhead and boot floor unpeeled. Two hours of petrol immersion did it all. Will have to re-seal the panel joints and make good with paint ... although there is an honest argument for resealing then leaving it as it is behind the boot card as a piece of history I could put into the file. I do not want to be in that position again on a filling station forecourt.

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I had a similar experience.  The price to get my old tank refurbished was more than the price of the Rimmers made in Taiwan version.  My sender was in good condition so I didn't need a new one.  The new tank came with a sender rubber seal which was a pleasant surprise, except I bought another one on the same order.  I had no problem fitting it except, like yours, my fuel line with old olive was a different profile to the one machined into the Taiwanese tank and fuel leaked into the boot.  Fortunately, I managed to find an olive so cut the pipe and refitted it without further problems.  Disappointing that the tank didn't come with an olive for the sake of a few pennies versus a lot of grief for the customers.

I used a screwdriver as a lever to fit the filler hose and this action dented the Taiwanese tank.  I needed a lot more pressure to remove the filler hose from the original tank and this caused no damage.   

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  • 2 weeks later...

Very pleased that It ended well!

The man-with- van from Warrington who returned with some gaffer tape  sounds to be one of those nice people who just quietly perform heart- warming, selfless acts of kindness. A society cannot call itself civilised without people who fill this role- vacancies  still exist.

Boring old  nanny stuff , but If you are serious re welding the old  petrol tank for barbecue use, please hesitate to  consider they can ,very occasionally  but rather dramatically, “go bang“ with bad outcomes,  unless they are really thoroughly purged of petrol vapour, preferably by steam cleaning...

Andrew

 

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On 08/09/2020 at 08:38, Badwolf said:

Years ago, I read about someone who filled the tank with expanding foam before cutting it up.

 Be wary.Such  an  anecdote may be construed as an endorsement of the method or advice. If it worked -fine, but that is far from being accepted practice.

I knew of a man with serious chronic  chest problems who contrived a method to continue smoking whilst on oxygen.-  He smoked a cigarette through a small hole he had made in his high  concentration oxygen mask.

Apart from being aggrieved that his fags burnt rather  fast  ( slower than   a sparkler but similar ), he  came to no direct harm from this.This doesn’t mean it is OK to do it and  I would still advise very strongly against  it!

These petrol tank explosions may be rare, but when they do happen they can be very nasty indeed.

 

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....thanks all......

I thought I'd write a quick update seeing as there is some very wise advice above on purging tanks and safety.

The tank was left outside until yesterday ...about 16 days... with all the orifaces open to the breeze, filler, drain and gauge sender. I'd read about plenty of horror stories with exploding tanks so was very cautious. I think my favourite was a bloke who attempted to get some grit out with a hand held vacuum cleaner and turned it into a jet engine that burned his garage down. No idea if that's a true tale but it's a good one.

After 16 days exposed to the air and originally very petrol smelly, I could not detect any fumes at all by nose yesterday. I filled and drained the tank with fresh water twice, placed it on a scaffold outside to dry in the sun. No smell at all, no film of fuel in the wash water. Confident it was safe to cut. After an hour I lit a diesel moistened rag and pushed it through the filler hole without issues. The rag burned out in about 5 minutes with an impressive chimney effect through the filler hole. NOTE ... I DO NOT ENDORSE THIS METHOD OR SUGGEST OTHERS TRY IT, I MERELY SUGGEST I WAS HAPPY THAT I HAD PURGED THE TANK OF FUEL IN THIS CASE ...

Took the grinder and cut the tank in half. I then discovered that inside are two thin steel baffles (see picture) to alleviate fuel slopping about. With a bit of wrestling I managed to break enough spot welds to pull the tank in two. On examination the tank was just about perfect inside, thick shiny steel with only the very slightest discoloration in patches you could call rust. That annoyed me. I'd wasted money on a new tank assuming mine was paper thin and leaking. The baffles are push fit with bent over tabs folded to sit against the tank walls. The two halves of the tank are then put together and sealed. The baffles are then spot welded from the outside as far as I can see. The penny then dropped. The pinhole leak I had was where a spot weld had failed allowing petrol to weep out. This had been patched years and years ago.

Just my take on it but what a bl**dy silly way to make a tank with baffles inside. Anyone else had a similar observation? Worth checking if anyone has a leaky tank. It should be a simple task to locate the spot welds, check each one and repair20200914_121019_resized.thumb.jpg.cde52279fc9604dd284edc0ba0586091.jpg and repair from the outside

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Why do think it's silly? It seems a perfectly reasonable method to me - pressed tin and spot welds. There's no particular reason a spot weld would rust through any quicker than a plain bit of steel, and in the 1960s a fuel tank was usually full of stuff that fairly effectively excluded water. It's only since we've had ethanol in our fuel that we get significant corrosion while the car is in use.

Anyway, that tank lasted 50 years! What more could you ask of it?

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Fair enough, each to their own opinion. I'm not saying I'm right, I'd just have done it a different way.

The spot weld hadn't rusted through, it had physically broken taking a tiny circular piece of tank with it. You may just be able to see this in the photo. I'm not saying it's a technique that doesn't work, it's just that the spot welds are something that can compromise the integrity of the structure. It would be perfectly possible to make an insert that could be simply placed in the tank to serve as a baffle without it rattling about. Just as easily, very similar baffles to the ones used could be slid into grooves with just a minor change to bolf halves of the pressed tank. They wouldn't move either.

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... and all of your suggestions involve more complexity either in design or assembly, which means more cost. Now build tens of thousands of them and watch your profits fritter away.

I don't know how your spot weld had managed to get broken. There's almost no stress on them in normal use.

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It's a perfectly academic debate...the whole thing is history now. However if you had designed the tank pressings in the first place to simply slot in two baffles, you could have done away with the bloke in the brown coat on the folding machine making the baffle tabs .... and the bloke in the brown coat wielding the spot welder. Much cheaper. 

My experience with mowers and diggers etc of welding bits that wear or break is that there is a portion of steel around the weld that becomes very brittle.

Just saying...

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I think your fuel tank investigations  are very interesting,Eddy, and thank you for sharing your observations.

I had no idea of the construction method.

Presumably that was a faulty spot weld right from the outset.

Maybe  the baffle flange was not fully flush with the tank wall  when the weld was made.

This could have the effect of thinning the tank wall with a   bit of weld bridging the slight gap between the tank and baffle.This could allow a movement between the two and though really tiny would eventually flex the weld off the thinned tank wall and - as you say, there is often a “brittleness” , for want of a better word, surrounding the weld which would aggravate this.

Another tank question that puzzles me 

Why  are some tanks so rusty with lots of pin holes yet  others of the same make,  model and year  - or often much older, can be relatively unscathed?

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In my professional life I'm a cricket groundsman. I get to deal with a lot of rather left field specialist machinery such as mowers, spikers, scarifiers etc. and because they get worked hard a certain level of in house mechanical work is required. Until recently we had an ancient Greens Griffen road roller for compacting the pitches run by an enormous 3 cylinder Lister Petter diesel engine. It was a handle hand crank which took a certain knack and a lot of grunt. I dreaded every spring as it was a beast to start again after the winter layoff and coughed and spluttered for half an hour first time out. I was talking to a farmer about this one day and he told me never to leave a tank half full over winter. Always fill it to the top. That prevents condensation on the inside of the tank wall. The spluttering was water which had run down the tank wall, settled over the take off pipe (lowest point) and been pulled through the line to the injectors. From then on I filled to the top and never had a problem again.

The same thing may be the problem with rusting. Some people habitually run their tanks half full or less. Some always refill to the top. Triumph Spitfires do a lot of standing about over winter. The random rusting could be due to condensation in tanks with only a bit of petrol in them. Just an idea....

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And modern, lead-free, alcohol containing fuel can absorb a lot more water, AND lose various additives some of whwich keep octanes up.

My enghones are built to a CR of 10.5, which is on the limit for 99 octane fule withiout pinking.     Some seasons ago, I started on  tank that had sat overwinter, and it pinked like mad!     A fill-up with new fuel and it went away.     I always use a 'fuel stabiliser' nowadays, and keep as little fuel in the tank as possible - not that I disagree with Eddy, just another way of managing the problem.

John

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Over the years I have learned to agree with what you say JohnD, it's what contractors hiring in plant call 'old petrol' that has lost most of the volatiles designed for modern small engines. They tend to drain the tank if it's a bad starter and refill. Someone also once told me to drain the tank on a 4 stroke engine before winter and refill in the spring. Modern engines such as Honda, Kubota, Subaru/Robin etc tend to have steel tanks protected from rust internally. I have also been told to drain a 2 stroke plastic tank from a chainsaw, hedgecutter, leaf blower or strimmer to remove all the oil, run with a dab of pure petrol for a minute or less then drain that and leave it dry overwinter. It is certainly true that a 2 stroke motor left for a long period with its 25:1 or 50:1 gums up badly as the petrol evaporates and leaves an oily residue and is a bu88er to start. I guess the bottom line with a strimmer or a Triumph Spitfire is the more you use it the more reliable and stable it is.

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back in the 70/80s we hung a silica gell sachet in the truck tank filler neck  with a long pig tail loop to show it was in there to combate moisture in long storeage

most got lost in the tank and made more problems as delivery drivers just popped the filler cap and away it went .. whats that   Oops !!!

pete

 

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