Cleaning the fuel tank need your opinion.

KBabcock

True Classic
So after I drained the fuel tank and it took hours for 3 gallons to drain, it was determined that the tank was gunked up. I pulled it today and saw a lot of gunk on the bottom and on the brass mesh sock. So I read everything I could find on cleaning the tank. Based on this here is my procedure.

- Get all the old gas out.
- pour 1/2 gallon of MEK (Methyl Ethyl Ketone) into tank and let it soak for 30 minute to 60 min.
- Pour out and was with dawn degreaser to wash the inside.
- Use pressure wash to assure all is clean.
- Dry out.
- Pour in some Etch & Prep (Phosphoric acid to neutralise any rust)

So I have some questions, any input on what I am using? I selected MEK because I watched a test by this guy who had and old fuel tank with an inch of dried varnish on the bottom, he pulled it out and cut up pieces to test how well different recommended solvents worked. He tested a dozen different solutions including gas, deiseal fuel, digresser, fuel treatments, commercial fuel tank cleaning products and others. In the end the three best where as follows in order from least to best. Acetone, Denatured Alcohol and the best was MEK which completely dissolved the gunk in 30 minutes. MEK is like Acetone on steroids.

The final question is do I use Fuel tank sealant, I had heard this are not good but wanted to ask what you think.

 
I discovered a biker's trick and used OxiClean. They like it because it does not damage paint on the tank. I was very surprised at how well it worked - took off all the crud and varnish. It is an all water based procedure and OxiClean is biodegradable. Also pretty cheap.
 
I used phosphoric acid to clean out my X tank and it worked very well. It originally had that thick goo covering the lower half but came out completely clean after the acid treatment (no other chemicals used). I think I documented this a little at one time.

As for doing a sealer coating after it is clean. There is a lot of disagreement on that. The vintage motorcycle and antique car restoration guys all swear by it. Most hot rodders and muscle car guys don't. In my opinion the success of it comes down to proper preparation - which isn't easy to really do correctly. In theory if you keep the cleaned tank full of fuel it shouldn't rust (unless possibly if it is full of ethanol based fuel in a wet climate).

A few years ago I purchased several different brands of tank sealers to experiment with but haven't got around to trying any of them myself. At that time everything I read indicated there were two that seemed to get the better reviews; the one sold by Northern Radiators and the one sold by Bill Hirsch. The ones I would not try are sold by Eastwood/Kreem, POR, KBS, to name a few. By the way, there are several that are just "relabeled" products from other companies. It appears there a some newer products out that weren't available when I researched it, so I have no idea about them. Also look at what the aircraft guys use (see the Aircraft Spruce site). But some of them may not be for automotive applications?
 
After my tank was clean, it appeared to already have some kind of clear coating inside. Water would just bead up on the surface and not form any rust even when left for a couple of days. I never heard that Fiat had coated the tanks and I'm pretty sure they are not made from stainless. A bit of a mystery.
 
They are definitely not stainless. The later tanks seemed to have a coating from the factory and I suspect that coating is what turned into the thick tar over time.

Here is a thread that Don started with plenty of discussion on cleaning methods:
 
Well I started with the the MEK today and am letting it sit overnight. I'm putting a filter between the tank and the pump so was trying to figure out how to remove the Brass mesh sock. It would be redundant with the filter and much harder to deal with then filter. Just need to figure out how to reach down their and remove it cleanly.

The phosphoric acid turns the rust into an inert layer of iron phosphate which prevents further rust so I feel OK skipping the sealer.
 
I had good luck with the Midwest Bayless replacement tanks when they were available. The lesson I learned was that the rust in old tanks causes havoc with the tiny idle jets in our Weber carbs even with monthly fuel filter changes because of the dusty red silt that collects in the clear visible aftermarket fuel filter.
 
Vick has a replacement tank is stock for $160. Was thinking about it but think I can get the current tank up to stuff. To me it all a financial decision whether to replace or not.
 
When I looked at cleaning the tank on my 124 I decided to just buy a new tank. The rust was bad enough the car wouldn't idle consistently even with two filters (one right after the tank before the pump and one right before the carb). I read too many bad stories online of resealing old tanks that I was worried of that going bad. I think if the car is going to be used consistently I would try only cleaning the tank and not risk the sealant. We are all on a budget but having a new fuel tank to save me from being stuck in the side of the road seemed to be the right choice at the time. It seems like this is one of the topics that doesn't have a great solution aside from buying a tank if available. You have to weigh your choices based on what your situation is.
 
As I read some of the above comments it occurs to me there are two factors at play when talking about cleaning the X1/9 fuel tank; rust, and the thick gooey tar deposit. Those are completely different in some ways, but also similar in others. What I mean is the thick tar can occur without any rust or metal damage (that's how mine have been). So cleaning those tanks can leave them in like-new condition. The same can be said for very mild rust ("surface rust") inside the tank. Both of those can be cleaned using the same methods we've discussed. On the other hand, if severe rust exists - such as it has eaten into the metal enough to cause holes, created a build up heavy flakes, covers 90% of the inside, or is otherwise really bad - then it may not be worth cleaning provided a reasonably affordable new replacement exists. In fact it might even be less expensive to replace it than to do a proper cleaning and coating of a badly rusted tank. So I think it depends on what your tank looks like inside.
 
trying to figure out how to remove the Brass mesh sock
All of mine were already partly gone. But enough of them remained to make it difficult to completely remove. I had hoped the acid cleaning process would simply dissolve what was left but it didn't. They are held onto the pick-up tube with a brass 'crimp band'. I tried to cut that band but I could not get a good bite on it due to it being at the bottom without much access. Then I tried to literally rip it off with a long rod but it proved to be rather tough. In the end I managed to tear off all of the mesh and leave the band in place. I used the long rod and formed a sharp hook in the end to grab the mesh with.
 
That had crossed my mind but if the cleaning is thorough it should be OK. Other have done it with success. It seems like some of the other issues I was reading about were from other components which would still effect the drivability even with a new tank. Again what you say makes a lot of sense but with the tank, shipping, tax you're around $200 plus so, I'll try the $20 worth of chemicals first.
 
I'm putting a filter between the tank and the pump so was trying to figure out how to remove the Brass mesh sock.
I wonder if the shooting your pressure washer into the larger output tube at the bottom of the tank would blow the sock off or at least clean it out a bit?
 
Back when family expenses exceeded family income, the thought of spending any money on Fiats was out of the question and in your situation I would have done anything I could to try and repair my gas tank cheaply. If that $200 for a new tank won't break the bank then it's a no brainer to me to get a new one. No worrying if your cleaning system worked, if the sock on the end of the pickup is clogged, rust won't start again, tank treating is compatible with modern gas. If you can afford it, get a new tank.

My spider has a new radiator and gas tank, two major issues I now don't have to worry about....especially since it's for sale!
 
Well the MEK soak is done, Used about .5 galons then poured it into a coffee can and let the solvent evaporate. I had about 1/4" of varnish in the can. Next I soaked it with Oxi Clean over night and here is where we are at. Next up is the phosphoric acid wash, the stuff I have is 40% concentration and will be used to convert any Rust to Iron phosphate. Thinking how long to let it soak in an area, maybe an hour or two. Sending unit is also shot, testing it with an ohm meter and nothing.

Here is the initial picture, not a very good picture took it with a scope.
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Here is the finished product before rust treatment. Looks like the brass mesh sock is gone which is good.
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Nice job so far. Looks like you got all that gooey crud out. Could you tell how much the gunk was removed by the MEK vs the Oxiclean, or vice versa?

Some of those rust spots appear to be a bit deep (difficult to tell in photos). No leaks? If not then check again after the acid treatment.

Phosphoric acid is a relatively weak acid (especially at that dilution) so it's action is slow. I think I let mine soak for several hours and still had to do it again. But I did not use another cleaning agent before the acid (as you did), so that would have slowed mine down. However don't be afraid to let it soak for a couple hours. The acid solution can be reused multiple times. Therefore if it still needs more cleaning then just pour it back in.

After the acid you'll need to rinse it. As much as I hate to introduce water to a freshly exposed metal surface, it is the easiest way with a large tank like this. You can flush it with a garden hose for a few minutes. Then make up a solution of water and baking soda for the final rinse. Do all of your flushing consecutively and immediately follow it with some denatured alcohol to absorb any remaining water. If you don't have denatured alcohol then try using a leaf blower to evaporate the water quickly. It will hide in the seams and crevices so dry it well. While the phosphate film that results from the phosphoric acid will act as a protectant, it isn't perfect. It results from the reaction of the acid and existing rust. Therefore areas that had no rust won't get the phosphate reaction and rust is always a possibility.
 
My experience with Ospho (phosphoric acid) is that it does not react at all with non rusty metal and just sits on it as an oily film.
 
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