vacuum tank restoration

[R.White]

I have decided to restore the original Stewart Warner vacuum tank. A previous owner had substituted an electric fuel pump and taken the feed to the carb via the tank. I presume this was done because without a regulator, the pump may well have caused the carb to flood. This set up worked well enough but I think must have been unsafe; even with the vacuum and vent openings blocked.

I removed the tank when it sprung a leak and it soon became clear that it had been repaired before. The unit consists of one container within another but the outer has rusted considerably but it may just be saveable. The two valves seem to work and all the mechanism is still in place. The two springs had failed and the float was full of petrol. There is a C spring attached to the float guide pin which has failed. I don't have another and I'm not sure if it is essential to the operation of the tank.

I decided on a rebuild when I received a quote for $600 plus shipping to the U.K. and taxes for a rebuilt unit from a reputable source.

Would anyone like to follow this rebuild?

Ray

[Guest 1930]

Sign me up!

[R.White]

Here in Britain, we have a similar vacuum tank which goes by the name of "Autovac". A friend and fellow enthusiast who lives nearby has one on his Alvis 12/50 and he insists that the vacuum system is worth keeping. Apparently, there is only one drawback and that is this wretched ethanol petrol we have these days. I understand that it is responsible for vapour lock with high under hood temperatures. I am informed that it would be advisable to plumb in the electric pump and a regulator with a separate control switch (all discreetly hidden from view) so that a boost can be applied if needed. My fear that the vacuum set up would lead to fuel starvation as the tank ran out on some of the hills around here has been roundly dismissed as apparently if the unit is working efficiently; i.e. no air leaks, it should not be a problem.

Edited October 6, 2012 by R.White (see edit history)

[Bob Zetnick]

Sign me up too! I have what looks like Stewart Warner fittings as part of the makeshift gas lines, but never had the tank.....bought a Stewart Warner tank in the 70's in order to replace an old fuel pump, but never did anything with it.....of course per this forum I should have bought a Kingston tank for my '29 DA to be original...still would love to learn more about a Stewart Warner rebuild!

[MikeC5]

If this one is constructed like the (somewhat) smaller Stewart on my 25, you may be able to repair leaks in the can by re-soldering. I suspect you could repair the float leak too and since it is so much larger than a carb float I wouldn't think a little extra solder would matter much. I think the springs are available. I have driven my car up a few decent hills and it hasn't had any issues but then the hills were probably not long enough to really test the tank cycling... I vote for going original Ray.

[Guest 1930]

If you provide some more pictures of what you are up against Ray I am sure you will get alot of different opinions of how to go about the repairs.

[R.White]

The first photo shows the inner cannister inverted with the flap valve disconnected. Fortunately, the valve seems to be in reasonable condition and can be used. The rust is not too bad and can be treated. Inside, the cannister is in pretty good shape. The last photo shows how badly corroded the inside of the outer tank is. So far, I have used a wire brush and emery cloth to remove the rust but it is the bottom of the tank where the real problem is. If you refer to my previous photos you will see that the drain plug has come away from it's holder. This had siezed solid but I have managed to free it with heat and a pair of grips. What I had not realised was that it consists of three parts - the barrel into which the threaded plug screws and a collar which is soldered onto the end. I was able to solder the fitting back into its holder in the bottom of the tank but this has revealed even more holes!

===============================================================

I have now managed to solder up all the holes (I hope) and the tank will soon be rust treated and ready for some ethanol proof tank sealant which I will order shortly. Meanwhile,I have drilled a small hole in the float and emptied all the stale petrol out (PHEW!) The hole has been soldered up and the float tested.

The two failed springs which operated the valve mechanism have been replaced. I have found it quite a challenge to get the right spring tension - too much and the float is unable to overcome it. I tested the springs by holding the top with the float dangling in a bucket of water. As the float is submerged into the water the upward pressure on the springs causes the valve mechanism to "flip". When the float is lifted out (imagine the petrol level dropping) the spring tension causes the valve mechanism to "fliip" back again. One valve operates the vacum control and the other valve is for atmospheric pressure and venting. One opens out and the other opens in so I was able to test them by blowing/sucking through the top fittings. They seem fine. The top would appear to be a replacement - the original pot metal tops (with the Stewart Warner patents on) often failed.

I welcome any advice and would particularly like to know if the C spring above the float which should bear on the linkage is essential as when I tried to correctly position mine, it snapped.

I will keep you informed of progress with more photos shortly.

Ray.

[platt-deutsch]

For restoring the outer tank, I would try the gas tank sealer kit from POR15. You could restore your gas tank at the same time and use some of the kit for the vaccuum tank.. I did the tank in both my 25DB and my 30 mod. A.. really works great if you do it exactly like the direction say.. The special cleaner and etching solutions in the kit are awesome.. No more crap comming out of the gas tanks..

[Pete K.]

Ray, good luck on your vacuum tank. Looks like it's really coming along. My '25 Stewart tank wasn't quite as bad as yours, but needed a lot of work too. That "C" snap spring must be there for a reason, I can't see it though...I looked at the pictures of the Stewart tank cut-a-way drawing in "our book" and was surprised to see it wasn't shown. I don't have the dedicated little reprint book on the Stewart tank. That may explain it. One very important part of that tank to work right is the complete sealing between the vacuum check valve and it's seat, up in the top of the tank cover. If you're done with the de-rusting of your outer tank, O.K.-- I was going to say that I found a good fix was to first get all oil/grease off the metal, then soak it in a can of "Evaporust". It really works well on rust but won't cut through any oily residue. Buy a "stand pipe" type fuel micro filter that Snyder's Antique Auto Parts sells and install it in the bottom outlet INSIDE the tank. The float WON'T hit the filter. I had to apply a thin coat of solder (twice), to this brass filter stanchion area since it's made for a Model A Ford gas valve but it tapped in nice and tight in my Dodge tank and works FINE. I'll never have the worry and heartbreak of foreign particles ever getting to my fuel bowl. EVER.

[kevin b]

Hi Ray

On my 28 victory I have the Stewart vac tank. I had a few issues with the float sinking. I had the por 15 tank sealer left over from my tank( which worked great)

The float fits just in side the litre can and I dipped that in and It has been good now for about 3 months. We have pulled some good hills in B.C. going from 1800 ft to 4500 ft . over 50 miles. I did get some vapour lock on the last long hill but it was 29c and it was a 5 mile long climb. As soon as we went down the other side it ran good again. I was in third most of the time but a few times into second. Went for a fall tour today for about an hours drive it was amazing all the colours. Good luck on the tank. They do work well. Kevin

[Pete K.]

The little filter I was describing to use in the vacuum tank is available at Snyder's Antique Auto Parts and it's part # is A-9193-T @ $4.00 each. They are in New Springfield, Ohio, USA. Phone toll free@ 888-262-5712. Don Snyder and the girls are very friendly to deal with and very helpful. From what I've seen in books, the Stewart tank was supposed to have a short standpipe (not a filter) inside the tank at the outlet, but I've NEVER seen one in any vacuum tank I've taken apart over the years. I'm betting it WAS there, a tiny steel pipe that probably rusted out and became dislodged several years (or decades) later. Anyway, for my 2 cents, this filter is the best deal going for many types of old cars, in many different application sites in a fuel system. Our old fuel tanks and vacuum tanks are getting harder to locate and they don't get any better with age. IF someone reproduces specific tanks someday, it will be a huge money layout I'm sure. Rust in the fuel system is probably the cause and effect of half the postings on the old car forums whereas a car won't run right or quit running.

[R.White]

Pete, this first picture shows the stand pipe. It is longer in reality than it looks here! I remember you mentioning before about fitting a filter to this and I thought at the time I would do the same - it seems logical. I will be getting in touch with the supplier. I looked into "evapo rust" and found that it is only available (through Ebay) in the States. The price was reasonable but the shipping costs, import duties and other taxes are horrendous; about 4 x the price of the original purchase. I have some suitable alkaline cleaner and a rust converter/killer called Fertan which I have used before on a different fuel tank.

Platt D. Mike, Bob and Kevin. thanks also for your input.

For me, the choice of tank sealant is between Por 15 and Tapox; which is 100% ethanol proof and I have also used before, but which is twice the price. I am pretty sure my fuel tank has been sealed because there is absolutely nothing caught in the tiny filter fitted to the inlet of the vac tank. The car used to be hired for weddings so I imagine needed to be reliable. It's also good to know that there is not much trouble from the vacuum tank on hills - we have some pretty challenging 4 in 1 hills in the Peak District!!

As you can see from the pictures, progress is being made.

Edited October 8, 2012 by R.White (see edit history)

[MikeC5]

It's looking really good Ray.

[R.White]

Thanks, Mike. You know until I found like minded guys on the forum, I would have had quite a lonely time with my old cars. I do have one good neighbour who has a nice collection of cars but now I am spoilt for choice !!

By the way, do you buy copper tubing in metric sizes or your traditional American standard sizes? It's nearly all metric over here and has been for quite a while.

[Guest BobD735]

Hi Ray,

I will be watching your posts very closely, regarding your Stewart vacuum tank restoration. My 1920 Chalmers has a Stewart tank, which needs restoration, along with everything else on the car.

Keep up the good work!

Bob

[MikeC5]

I know what you mean Ray. Most of my neighbors don't seem too interested. We do still sell the copper tubing in inch sizes here (at the big box stores anyway). I'm not sure about auto part stores but I suspect some might have both.

[Pete K.]

Nice job on that tank Ray! They really are very dependable when restored. I never had a problem with one on a hill either. It's funny you mention about the copper tubing! I just bought a two foot length of it yesterday at my local hardware store for use on the Dodge. I simply asked the plumbing manager there for 1/4" copper tubing. It's inside dimension is 1/4". I measured the outside diameter with my micrometer just now and it shows .312" I tried using a steel scale and it seems to be pretty close to read 5/16". Sorry this is not in Metric's. I seem to be having a real problem finding the steel flare fittings that are used on the Dodge carb & lines, so be careful when you fiddle with them!

[R.White]

Thanks guys. The one problem that I keep coming up against (and I have mentioned it before) is that of threads. I bet those pipe fittings are the same. We used British threads for the most part in old cars i.e. Whitworth and B.S.F although in some engines, like Morris, metric can catch you out. Later British cars used U.N.C / U.N.F and then we got sucked into Europe and everything became metric. I don't much like Metric. Strangely, my Drummond lathe has a metric option and that was built in Guildford, England in 1921.

My point is that none of my nuts and bolts (of which I have a vast selection) will fit the Dodge. If you could advise me what to look for in terms of taps and dies - what you used in America back then? What is it I should ask for? If I want to buy American nuts and bolts, how are they described?

Not finding a bolt to fit drives me nuts!!

[Guest 1930]

Thanks guys. The one problem that I keep coming up against (and I have mentioned it before) is that of threads. I bet those pipe fittings are the same. We used British threads for the most part in old cars i.e. Whitworth and B.S.F although in some engines, like Morris, metric can catch you out. Later British cars used U.N.C / U.N.F and then we got sucked into Europe and everything became metric. I don't much like Metric. Strangely, my Drummond lathe has a metric option and that was built in Guildford, England in 1921.

My point is that none of my nuts and bolts (of which I have a vast selection) will fit the Dodge. If you could advise me what to look for in terms of taps and dies - what you used in America back then? What is it I should ask for? If I want to buy American nuts and bolts, how are they described?

Not finding a bolt to fit drives me nuts!!

Ray I would purchase a tap and die set ( cheap ) from E-bay. Depending on how large of a set you have you will not only have the tools but also give you the measuring device to get the correct pitch and count of what you might come up against in most cases.

SAE Standard American thread and Metric will be included in a decent set

[R.White]

Thanks Jason. "SAE Standard American thread" what does SAE stand for please?

Also, is it different for pipes? Here we have BSP British Standard Pipe which is still used in pneumatic and hydraulic installations but I expect metric will take over here too.

[i have a wide range of metric taps and dies and also imperial - top quality stuff inherited from my Dad - but no American sizes. Has the "Standard American thread" system remained unaltered from the start? If so you guys are lucky. We have also had several changes in spanner (wrench) sizes. When I was clearing My Dad's garage I unearthed dozens of open end and ring spanners which have been obsolete for 50 years! Useful to anyone with a pre war British car! We adopted the American AF (across flats) sizes post war but it's all metric now.]

I will seek out a tap and die set - "Standard American Thread"- on Ebay .com.(as opposed to Ebay U.K.) I don't buy cheap tools - a false economy in my view - but as usual it will be the shipping, duty and taxes which will make it cost so much. No problem though.

Ray.

Edited October 10, 2012 by R.White (see edit history)

[Guest BobD735]

Hi Ray,

SAE stands for Society of Automotive Engineers.

Bob

[R.White]

Thanks Bob, I didn't know that.

Jason, when I said " I don't buy cheap tools - a false economy in my view....." I am sorry if it sounded pompous; it wasn't meant like that. it just came out wrong and in fact is not always the case. I appreciate you were considering not just the costs but the amount of use I would give it with having just the one American car. Also, it's not always the case (but often is) that cheap price equals poor quality. I bought a 3 jaw chuck made in Poland. The quality was every bit as good as a British made tool but less than half the price. I was so impressed, I went back for the 4 jaw version!

Ray

[Guest 1930]

I dont get offended Ray easily, like Bob said SAE is Society of Automotive Engineers and they are the people that coordinate the development of technical standards.

Google any phrase you can come up with and learn more than you would prob. want to know concerning thread size, pitch, changes ect.

Have fun

[Guest BobD735]

Hi Ray,

To help you identify American thread sizes, there's a precision threaded tool called a Screw Checker. I purchased one that identifies SAE/Inch screws from #1 to 5/16". There are also Screw Checkers for metric threads.

Go on Google and type in Screw Checker.

Bob

[R.White]

I see what you mean, Bob. A useful tool. I have thread gauges for all the British and metric ones - toothed steel blades that fold up like feelers.

As I thought, UNF and UNC are American threads which we have used over here for years prior to metric but the question is -: "are they different from Standard American threads? "

As it happens, I have taken the steel flare fittings from the electric fuel pump and will re use them to attach the pipe from the nipple on the carb to the elbow on the vacuum tank. The fuel lines can be connected with a straight compression fitting. (hopefully)

Ray.

[Pete K.]

Ray, the compression type fittings with the brass nipples work just fine. My Model A's use them originally to the carb & so forth with no leaks ever. Two notes here-- set the nipple no more than 1/8" from end of copper line. 3/32" is ideal, and snug up the up compression fitting. You should replace the nipple and cut off the "used" end of the line a bit if you remove the line at any time later. Although I preach this, I'm guilty of re-using these fittings if I change out a carb. Just don't tell anyone. I found a very good source of hardware for old cars, both US & Metric, a place called "McMaster-Carr". Google them and see the thousands of great things they sell!

[Guest BobD735]

Ray,

Regarding your question about the American UNF and UNC. I checked my copy of SAE Handbook, and I quote the following:

"In the British Standard 1580-1953 for Unified Screw Threads, the (American) Unified coarse thread series designated UNC and the fine thread series designated UNF are the only series recognized as standard;"

This applied to both Britain and Canada.

Bob

[R.White]

Hey Pete - what you guys call a nipple we call an "olive" . What we call a nipple (grease) you call a "zerk". No wonder I get confused!

I tried to access the McMaster Carr site; put in all the info to log in but was left hanging..... That aside, if they are like many other U.S. firms unless you pay in dollars they won't want to know. This even happened with the restoration guy who quoted me $600 plus shippng (and taxes) for a refurbished vacuum tank. I expect he thought I would go away at the price - if I couldn't do anything with mine and no other tanks had been available, I might have been forced to pay up; so that would have been his loss!

With cheap items, like the stand pipe filter for example, the problem is worse unless they advertise on Ebay and take paypal. (I have made up my own stand pipe filter and will post pictures of this particular work of art shortly. chuckle). Thankfully for most things, Myers are geared up to sell into the U.K.and Tom and Cindy are also great to do business with.

Bob,

I have worked out that the fitting which screws into the carb/inlet manifold for the vacuum take off is most probably UNF or UNC. Fortunately, these are the American threads which took over from BSF and Whitworth over here after WW2. What I still don't seem to be able to find out - even with Google - is whether Standard American thread is something different again?

It's not a problem, just a question I would like to have the answer to.

[1936 D2]

Ray: I think there may be a slight misunderstanding on this thread. Jason stated in post #19 that there was a thing called a "Standard American thread" using capital letters which gives the impression this is a particular "thing". The thread types are known over here as "metric" and "standard". The "standard" threads are defined by the SAE (Society of Automotive Engineers) and are what you are familiar with as the UNC and UNF fractional numbered thread design as described by "BobD735" in post #27.

So to clarify, there is not a "thing" called a "Standard American thread". That is just a vernacular. Threads are currently defined by the SAE as "standard" threads and the SAE also recognises the "metric" thread as a type of measurement standard.

One of the common places we buy tools over here is Sears. Check this page ( Craftsman 107 pc. Tap and Die Set, Carbon Steel, Metric/Standard - Gifts - By Personality - DIY-er ) for an example of a set of tap and dies that covers most all of the common automotive sizes.

Also, on the US version of the page near the middle of the "Overview" tab, you would find a link ( http://c.shld.net/assets/misc/CRFTTapnDieSets.pdf ) that helps with the listing of all the sizes in the tool set on a PDF document. There you will see the SAE sizes AND the metric all listed together.

It would be interesting to know if "pipe threads" work this same way concerning American pipe thread descriptions and BSP.

Edited October 10, 2012 by 1936 D2 (see edit history)

[DavidMc]

Ray,

I just came across your thread and would like to make a few comments.

Firstly I have vintage cars all with Stewart Warner vacuum tanks and have done 10's of thousands of kilometres in them, they work fine, an electric pump feeding into the vac tank is not the way to go - more on that below.

Vapour lock due to ethanol is an issue but the ethanol only makes it marginally worse, vapour lock can occur with all fuels, the subject has been extensively discussed on this forum as I am sure you are aware. The main fixes are heat shields and adding kero or diesel to the fuel and a bypass electric pump however even those comments will be controversial to some.

The first photos of your tank seem to show that it has a brass top which is a very good thing and indicates it may have been replaced. All of the originals I have seen have pot metal (die cast) tops and they can cause problems and are best replaced with new aluminium ones - let me know if you need the contact.

I do not profess to understand the function of that 'C "spring however I have a friend with a '28 Dodge who had the " C" spring fail. The vac tank stopped working and was fixed as soon as a new spring was installed.

I was interested in your problems with threads, I had the same issues when I restored my last car and never found the thread size for one of the top connections, I finished up making a new connector to fit the thread. However I am sure it is a standard thread, I just failed to find a mating fitting.

I have just fitted an electric pump to my car in the fuel line at the rear, it feeds directly to the carb, bypassing the vac tank with one way valves to prevent reverse flow. It is operated by a switch and is intended for use only when vapour lock occurs. I recently had occasion to test it when I experienced vapour lock in heavy stop start traffic on a warm day. I switched on the pump and the vapour lock momentarily stopped then the car started missing and stopped. When I opened the bonnet (hood) I found the float had dropped the carb was flooding. The electric pump was still running and the float was not lifting and shutting off the fuel. I had to cool the carb down before the float would shut off the fuel supply and get going again. So another vapour lock mystery to solve, the current theory is excessive vapour pressure in the float chamber depressing the float - despite the fact that the float chamber has a small vent. It has been suggested that it needs a larger float chamber vent to relieve the vapour pressure caused by the vaporising fuel in the hot carb..

Sorry if I have drifted a little off your thread with the vapour lock story but the message is stay with the vac tank and electric pumps are not necessarily the answer to all problems.

David

[Guest BobD735]

Hi 1936D2,

You did a good job explaining the "Standard American Thread" to Ray.

Thank you,

Bob

[R.White]

1936D2. You have answered my question, thanks. Fortunately, I have a comprehensive range of taps and dies for UNF & UNC. (I also have solutions for BSF, whitworth, metric, BSP and BA.) It could well be that your pipe sizes are different because as anyone who has handled BSP will confirm, it is a most peculiar (strange) system. My Dad was a pneumatics and hydraulics development engineer so thought nothing of it; but to me, BSP remains the odd one out.

David thanks for your interesting input. There is no substitute for experience!

Yes, I do have a replacement brass top - the tank I am restoring has been repaired before but at some time has been superceded by an electric pump feeding into the tank with the other openings blocked. This is a dangerous practise, in my view, but I guess the reason it was done was to provide enough resistance to the pump. I think either one fits a low pressure pump or a pressure regulator to prevent flooding at the carb. You only need 1 psi. In my experience, there are "pushers" or "pullers" when it comes to fuel pumps. If a "pusher" is fitted under the hood, there is bound to be trouble. I notice you have yours fitted at the rear of the car. I was planning to do just as you have with non return valves and a seperate switch for emergency use if vapour lock occured but you have made me rethink my plans. I was under the impression that ethanol was the primary cause of vapour lock because it has increased the volatility of petrol; making under hood temperatures higher and, as a double whammy, cause an increase in vapour unable to escape. The suggestion in the mechanic's workshop manual, of making a very small hole in the inlet manifold /vacuum pipe connector seems counter intuitive to me - although that is where the vapour lock is supposed to be - I would have thought any leak in the vacuum system would be detrimental to the vac' tank pumping system....

Perhaps the most worrying thing to my mind, are your comments regarding the "c" spring which sits at the top of the float and comes into contact with the valve operating mechanism. Like you and Pete, I can see no essential purpose for this spring. The only thing which it could do, from what I have seen by studying it at length, is to iron out any sloppiness or wear in the various linkages. This could help the mechanism to operate more smoothly, but I fail to see how it would have a fundamental effect on the working of the vacuum tank. No doubt someone will be able to explain it's true function and have a reason why it is not present in various other vacuum tanks. There is no "c" spring visible in the exploded diagram of a Stewart Warner tank either in the manual or book of information.

Ray

Edited October 10, 2012 by R.White (see edit history)

[DavidMc]

Ray,

I did not want to hijack your thread and turn it into another "Vapour Lock " discussion however you might be interested in the attached web site which explains the changes that have occurred to the volatility of fuel. My experience with vapour lock started in 1976 and it is mentioned in literature dating back to the 1930's and maybe earlier, long before ethanol became an issue. Ethanol has just made it worse in my opinion.

As for the pressure regulator after the electric pump I intended to fit one but the very well known US supplier of the pump told me that he had the same pump on his Packard and it worked fine without a regulating valve so that is how mine is presently set up and it does not flood under normal operation only when vapour lock has occurred. I will fit a pressure regulator because the delivery pressure to the carb from the electric pump is much higher than the gravity feed from the vacuum tank.

My car has the vacuum tank right over the exhaust manifold, maybe your Dodge has a better arrangement and the fuel supply does not get as hot however under bonnet heat is certainly a big factor.

Lets hope someone can explain the function of the "C" spring , I agree with you it seems to do no more than take up slack.

David

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[Guest 1930]

Ray I dont think ( unless I missed it ) that you made clear where the C spring is. I have no idea what you are referring to, might help if it were more clear

[DavidMc]

Jason,

The "C" spring can be seen immediately above the float in the drawing on page 4 of the attachment.

David

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[R.White]

Jason, the "c" spring is a simple piece of very thin spring steel about 1/4" wide. It has a hole in either end through which the float - to - lever mechanism connecting pin passes. The bottom of the spring rests on the top of the float and the upper part of the spring places tension on the mechanism above. This tension is maintained regardless of the position of the float and valve mechanism as it goes up and down in the inner chamber. The "c" spring, however seems not to have any influence on the valve operation which is controlled by the action of the two parrallel springs which "flp" the valve mechanism about a pivot point. The "c" spring seems only there to take up any slack in the mechanism which may be present due to wear etc. At least that seems to be the general concensus. My "c" spring snapped when I tried to position it correctly and the mechanism would require dismantling if it were to be replaced.

Ray

[Pete K.]

Here's a photo of my spare unrestored Stewart vacuum tank innards, showing the "C" spring in question here. It is brass, not soldered to any part, but Ray, it has a tiny "wave" at the top whereas the linkage rides on, creating a stiffer "fit" to that linkage and the float. From what I can see, the purpose of that C spring is to remove any excess play in the riveted point at float and linkage AND it seems to keep the float from rattling around in it's inner tank. I would try to replace that blumin' thing.--Best, Pete.

[R.White]

Thanks, Pete. Yes, I see that it is indeed made of brass.

Thanks to everyone. I am keeping my fingers crossed that someone will have a spare.

Ray.

[Guest 1930]

Yes, I would not attempt to put anything back together unless it were there, you have to remember that it cost money ( big money ) to put it there and if it were not needed than.....you get my point

Thanks for the pics, I am only vaguely familiar with Stewart, Kingston tanks are much simpler

[1936 D2]

Pete K. - Would you be able to measure the "C" spring's tension for that spring in your photo sometime? It does look like a fairly simple spring design and may be able to be re-manufactured. Sounds like many people have the same issue of "spring breakage" of this thing so a repo part may be in order. Dimensions can be easily obtained but the tension is the current unknown.

Maybe use a "Points Spring Tension Gauge" to test it out?