Need to clean fuel tank - AGAIN

dllubin

dllubin

Don
About 6 weeks ago I cleaned my gas tank by filling it with detergent and water, draining it, pressure washing it, drying it with a blower, and then vacuuming the inside. A little over a week ago I put about 2 gallons of gas in it after the engine was back in. Over the course of a week or so, I ran the engine a number of times to get the car ready for its first drive in several decades. I went to start the car today and no go. I squirted a little gas in the carbs and it ran for a few seconds and died. I then noticed that the insides of both the pre-pump filter (Thanks Dr. Jeff for encouraging me to add it) and the post pump filter were totally black after being spotless yesterday. The fluid inside the filters and lines is a very dark, varnish-like, viscous mess.

My only hypothesis at this point is that letting gasoline sit for a week in the tank must have dissolved some gasoline soluble stuff on the sides of the tank and allowed it to go into solution. I siphoned out the remaining gas down as far as the fuel pickup tube would go and a little over half way clean looking gas started coming out again. I plan to remove the sender/pickup again, siphon out the remaining gas, and see what is going on inside.

Any advice on further cleaning? Gasoline seems to be an effective solvent but as I found out after emptying out the tank of 23 year old gasoline a few months ago, it is hard to get rid of as most the places around here that take motor oil won't touch it.
 
remove the tank and turn it upside down. I did that on a car I just got and was AMAZED at how much junk came out of it. (then I noticed some rather large holes from rust in the tank.

IMG_2046.JPG
 
Rod Midkiff said:
remove the tank and turn it upside down. I did that on a car I just got and was AMAZED at how much junk came out of it. (then I noticed some rather large holes from rust in the tank.

View attachment 14447
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That would have been much easier a few days ago when I had the car several feet in the air. Actually, after the initial cleaning it was pretty clean as far as rust and particulate matter. I did notice some varnish-like substance on the walls, particularly below the level where a little bit of gas was sitting over 20 years. If it was on there after the pressure wash, it must have been sticking real well but apparently it is gasoline soluble.
 
What fuel lines are you using?

A newer fuel may be eating the interior of your fuel lines creating the gunk you see in the filters. Just a thought. Old fuel line doesn’t like modern fuel.
 
kmead said:
What fuel lines are you using?

A newer fuel may be eating the interior of your fuel lines creating the gunk you see in the filters. Just a thought. Old fuel line doesn’t like modern fuel.
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I'm using all brand new Gates Barricade lines. When I started to siphon the tank, I was pulling it right off the metal feed tube in the sender and the crud was still there. I did manage to flush out my new lines and fittings with fresh gas and they seem to be fine. I plan to pump some fresh gas through the fuel pump tomorrow. I pulled the carb inlet screens but it doesn't look like the double filters let any dirt (or gasoline) that far.

As far as the tank goes, I'm trying to find a creative solution other than filling it up with gasoline, letting it sit a few weeks, and then draining it. I plan to pull the sender off again to get a better look at what I'm dealing with before proceeding.
 
The best method that I have found for cleaning old fuel tanks is to remove the tank (sorry) and use a phosphoric acid solution (roughly 30-40 percent). Fill the tank with the solution and let it soak for a couple hours and then rinse and dry. The acid will remove all old varnish, any residual rust, and any "tar" from old rubber products that melted from the fuel (as Karl described). That tar can build up inside a tank that has (had) a return fuel line, or from the rubber gasket at the sender, or the rubber connection hose to the filler cap, or if anything rubber ever fell into the tank, etc. That stuff is very difficult to remove and will continue to foul the system. Another great benefit to using phosphoric acid is it creates a phosphate layer that acts as a rust barrier, preventing future rust issues. When you cleaned it the first time, then rinsed it, the rinse water will start new rust forming immediately (assuming you rinsed with water). Note that some phosphoric acids are sold already diluted.

Another option if you can't get phos. acid or don't like working with caustic substances is to take it to an old fashion radiator repair shop. They can 'hot tank' it (like they did to radiators when they were made of metal).

In my opinion trying to clean it without removing the tank will not yield good results and you will end up spending a lot more in replacement filters.
 
Dr.Jeff said:
The best method that I have found for cleaning old fuel tanks is to remove the tank (sorry) and use a phosphoric acid solution (roughly 30-40 percent). Fill the tank with the solution and let it soak for a couple hours and then rinse and dry. The acid will remove all old varnish, any residual rust, and any "tar" from old rubber products that melted from the fuel (as Karl described). That tar can build up inside a tank that has (had) a return fuel line, or from the rubber gasket at the sender, or the rubber connection hose to the filler cap, or if anything rubber ever fell into the tank, etc. That stuff is very difficult to remove and will continue to foul the system. Another great benefit to using phosphoric acid is it creates a phosphate layer that acts as a rust barrier, preventing future rust issues. When you cleaned it the first time, then rinsed it, the rinse water will start new rust forming immediately (assuming you rinsed with water). Note that some phosphoric acids are sold already diluted.

Another option if you can't get phos. acid or don't like working with caustic substances is to take it to an old fashion radiator repair shop. They can 'hot tank' it (like they did to radiators when they were made of metal).

In my opinion trying to clean it without removing the tank will not yield good results and you will end up spending a lot more in replacement filters.
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Dr Jeff:

Doesn't a full tank at 30-40% concentration require quite a bit of acid? Do you have any recommendation on sources or specific products? I've seen a number of products that don't disclose concentration and seem to be sold more like phosphoric acid cleaners rather than chemical grade phosphoric acid. I watched some YouTube videos on cleaning gas tanks and they used everything from muriatic acid to toilet bowl cleaners.

I was also wondering if removing the tank is a requirement. Last time I cleaned the tank in situ, I was able to get a pretty good flow rate of water going through it that carried away any particulate matter as well as the detergent. I'm wondering if this approach would work with phosphoric acid?

Thanks,

Don
 
Personally if a new tank was available I would go that route. For my son's RX7 I used Eastwood's gas tank cleaner and POR sealer. That was about 6 years ago and the tank is still in service without issue. Yes you need to remove the tank to do the cleaning and use the POR sealer which takes about 4 days to cure. The whole process will take a week from cleaning to rinsing to drying, Midwest Bayless has a new tank no welding required which is another issue in the past that I have been forced to do with older gas tanks.

TonyK.

On route home from FFO 2018 Orlando.
 
TonyK said:
Personally if a new tank was available I would go that route. For my son's RX7 I used Eastwood's gas tank cleaner and POR sealer. That was about 6 years ago and the tank is still in service without issue. Yes you need to remove the tank to do the cleaning and use the POR sealer which takes about 4 days to cure. The whole process will take a week from cleaning to rinsing to drying, Midwest Bayless has a new tank no welding required which is another issue in the past that I have been forced to do with older gas tanks.

TonyK.

On route home from FFO 2018 Orlando.
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The tank is in pretty good shape as far as rust goes. If I can get the varnish like substance out, it should be good to go so my last choice for now would be replacement. I just viewed a video of the Eastwood product being used to clean and coat a tank on YouTube. Sounds like it worked for you. If it turns out my tank has serious issues, I'm with you on buying a new one.

Have a good trip back!
 
Some additional thoughts.
The concentration of acid available for sale must be listed on the label (if it is indeed acid and not just a "cleaner" using the name 'phosphoric'). Look at the little box with the 'contents' or at the bottom of the label.
The dilution percentage you use will determine how long it will take to achieve a good clean. So if you only get a gallon container of acid (the local Home Depot type stores here sell it, I think under $15), and dilute it with say 6 gallons of water, then it will need to sit roughly twice as long in the tank than if you dilute it with say 3 gallons of water. I'd suggest at least 2 gallons of acid if you can.
If the tank is removed then you don't need to completely fill it; you can fill half of it and seal all openings, then when that half is done turn it upside down and do the other half.
The acid can be reused over and over, so save it after cleaning the tank for future needs. It is the best way to clean and treat any rusty metal (including bodywork).
Working with acid can be hazardous to you and the car, so I would not try to fiddle around with it while the tank is in the car...just suck it up and remove the tank again. ;) Plus it will help to 'slosh' it around as it soaks, which isn't really possible to do while in the car. Wear the proper safety gear.
Phosphoric acid is much milder than muriatic acid. Muriatic will eat right through the tank (so will phosphoric if it is a very concentrated solution and you leave it there long enough). Drain cleaners, etc are (typically) caustic lye, also extremely aggressive. I would not use anything too strong.
Other products like Eastwood, etc are either pre-diluted phosphoric acid (at many times the cost) or less effective approaches. They may get the job done, depending on how bad the tank is, how hard you work at it, and how long you leave it. But I've found the simple method described above works very well, the inside of the tank will look like new and there will be no need to "coat" it (keeping gas in a tank will also help prevent rust).
The tank "liners" (coatings) have very mixed results; a couple seem to work pretty well but most create a bad situation when they start to break down and turn to gum or peal off in sheets. As mentioned, phosphoric leaves the metal surface with a protective barrier that is a chemical process with the metal itself, not a 'coating'.
These are my opinions and thoughts. Please decide what works best for you. :)
 
OK buddy, this morning I pulled the tank on one of my X's for cleaning. This car is VERY rusty so every bolt and clamp faught me. Plus it is a FI car so it has more hoses and connections than a carb'y car. The removal took roughly 45 minutes (I have physically limitations and work at an extremely slow pace). Then I began the initial cleaning process - draining the residual fuel, quick inspection, and flushing with tons of water (using a high pressure nozzle on the hose). The acid clean will come tomorrow. The amount of crud that came out was amazing, but more on that in a minute. First some additional info for your benefit.

I was reminded of a few things I neglected to mention earlier:
1) When you drain the tank there is still about 1.5, maybe close to 2 gallons remaining that won't come out without inverting the tank (with the fuel level sender removed), or a really strong (and petroleum proof) vacuum pump to suction it out. Even with the tank inverted it is difficult to get all of it out because of the contours of the tank's shape and connection of the fittings/filler tube, etc. It took a lot of shaking and jostling to get most of the liquid out. I really don't see how you could do this with the tank still in the car. Especially after rinsing with water, you would end up with a fair amount of it left inside.
2) As far as physical damage (corrosion, rust, etc) to the actual metal walls of the tank, the worst area of it was the upper third or so...not the bottom. That's because when the tank has fuel it it, rust won't form (as much). Left with say 2/3's a tank of fuel, and the upper third is exposed to water vapor and condensation and will rust. This area of the tank would be difficult to strip completely clean with the tank still in the car - you would have to completely fill it with something strong enough to etch the stuff off the walls. And petrol won't work, otherwise it would already be clean from normal use.
3) With the tank removed from the car and after flushing with water, I was able to give it some "banging", shaking, pounding, tapping on the concrete, etc while it was inverted to loosen a BUNCH of built up crud that would not come off with just the flushing. Like I said the acid treatment will come later, but removing as much of the physical contamination as possible gives the acid a much better chance to get down to the surfaces of the tank. Some suggest putting a section of chain inside and shaking it violently to help break up the accumulation. All of this can't be done with it in the car.

So what about the crud inside it?
That residual amount of fuel that I said stays in the tank when you drain it really isn't fuel, more like poo. With water being heavier than petrol the bottom of the tank (below the fuel pickup level) always has some water (that's why the fuel pick up isn't located at the very bottom). If you are lucky and it hasn't rusted the tank, then you will certainly have fungus, mold, and all sorts of living organisms that you do not want to know what they are. It had formed a layer about an inch thick all along the bottom. This was a semi hard, spongy, crusty growth the came out in chunks. And it was very stubborn; hince all the banging and pounding I mentioned. More and more kept breaking up and falling out when I inverted the tank and shook it violently....again, something that could not happen in the car. Here is a little sample of that crust the was on the bottom:
001.JPG


The corrosion on the side walls (mostly upper third) still did not come loose. That is where the acid treatment will come to play. Actually I should do the 'chain inside the tank' agitation first. I know you said your tank wasn't too rusty (certainly not like this one), but I would bet there is some sort of foreign matter built up inside that will take a great deal of physical and chemical effort to eliminate. And to be clear, I am not criticizing the cleaning job you did. It sounds like you were quite thorough. I am however trying to convenience you the the tank must come out in order to really get it completely clean, and avoid having more of the contamination you found.

Just for fun, here is a shot of the fuel level sending unit:
003.JPG


I'll report more after the acid portion of the cleaning process is done.
 
Dr.Jeff said:
OK buddy, this morning I pulled the tank on one of my X's for cleaning. This car is VERY rusty so every bolt and clamp faught me. Plus it is a FI car so it has more hoses and connections than a carb'y car. The removal took roughly 45 minutes (I have physically limitations and work at an extremely slow pace). Then I began the initial cleaning process - draining the residual fuel, quick inspection, and flushing with tons of water (using a high pressure nozzle on the hose). The acid clean will come tomorrow. The amount of crud that came out was amazing, but more on that in a minute. First some additional info for your benefit.

I was reminded of a few things I neglected to mention earlier:
1) When you drain the tank there is still about 1.5, maybe close to 2 gallons remaining that won't come out without inverting the tank (with the fuel level sender removed), or a really strong (and petroleum proof) vacuum pump to suction it out. Even with the tank inverted it is difficult to get all of it out because of the contours of the tank's shape and connection of the fittings/filler tube, etc. It took a lot of shaking and jostling to get most of the liquid out. I really don't see how you could do this with the tank still in the car. Especially after rinsing with water, you would end up with a fair amount of it left inside.
2) As far as physical damage (corrosion, rust, etc) to the actual metal walls of the tank, the worst area of it was the upper third or so...not the bottom. That's because when the tank has fuel it it, rust won't form (as much). Left with say 2/3's a tank of fuel, and the upper third is exposed to water vapor and condensation and will rust. This area of the tank would be difficult to strip completely clean with the tank still in the car - you would have to completely fill it with something strong enough to etch the stuff off the walls. And petrol won't work, otherwise it would already be clean from normal use.
3) With the tank removed from the car and after flushing with water, I was able to give it some "banging", shaking, pounding, tapping on the concrete, etc while it was inverted to loosen a BUNCH of built up crud that would not come off with just the flushing. Like I said the acid treatment will come later, but removing as much of the physical contamination as possible gives the acid a much better chance to get down to the surfaces of the tank. Some suggest putting a section of chain inside and shaking it violently to help break up the accumulation. All of this can't be done with it in the car.

So what about the crud inside it?
That residual amount of fuel that I said stays in the tank when you drain it really isn't fuel, more like poo. With water being heavier than petrol the bottom of the tank (below the fuel pickup level) always has some water (that's why the fuel pick up isn't located at the very bottom). If you are lucky and it hasn't rusted the tank, then you will certainly have fungus, mold, and all sorts of living organisms that you do not want to know what they are. It had formed a layer about an inch thick all along the bottom. This was a semi hard, spongy, crusty growth the came out in chunks. And it was very stubborn; hince all the banging and pounding I mentioned. More and more kept breaking up and falling out when I inverted the tank and shook it violently....again, something that could not happen in the car. Here is a little sample of that crust the was on the bottom:
View attachment 14529

The corrosion on the side walls (mostly upper third) still did not come loose. That is where the acid treatment will come to play. Actually I should do the 'chain inside the tank' agitation first. I know you said your tank wasn't too rusty (certainly not like this one), but I would bet there is some sort of foreign matter built up inside that will take a great deal of physical and chemical effort to eliminate. And to be clear, I am not criticizing the cleaning job you did. It sounds like you were quite thorough. I am however trying to convenience you the the tank must come out in order to really get it completely clean, and avoid having more of the contamination you found.

Just for fun, here is a shot of the fuel level sending unit:
View attachment 14530

I'll report more after the acid portion of the cleaning process is done.
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I'm interested in how you make out on the acid portion. From the looks of what came out of your tank, you and I may be dealing with somewhat different dirt problems. When I did my initial cleaning, I took the following steps after removing the sender:

1. Siphon tank empty, get residual gas with rag.
2. Fill tank with water and detergent (Pinesol equivalent) and let sit overnight.
3. Drain tank with siphon.
4. Pressure wash tank through sender hole. Siphon as necessary.
5. Fill tank while siphoning. Set fill rate to match siphon rate. Run ~30 min. The siphon is effective at pulling the sediment off the bottom of the tank so letting it run a while pretty much gets everything.
6. Blow tank dry through filler with 240 mph, 800+ cfm backpack blower.
7. Vacuum residue (not much, if anything there after blower).

After the above, I inspected the inside of the tank and it looked pretty good except for this varnish like substance on the sides, up to the level of where the residual fuel was likely sitting for decades. It was affixed very securely to the sides of the tank and not at all wanting to come off. I have a feeling that stuff soaked for a week in the gasoline and became soluble. As far as the solids that came out through the siphon, it was all a super fine powder like substance with a light coffee like color. My guess is a combination of rust and small particulates from the tank and roughly 4,000 gallons of fuel that went through it. I found nothing like what is in your photos. As far as the sender unit, it was coated with a slightly slimier version of the varnish stuff. It cleaned up like new with scrubbing and solvents. I cleaned the resistor contacts with DeoxIt for good measure.

The first thing I am going to do is take the sender off and have a look inside. I am curious to see what is left inside. When I siphoned the remaining gas out, I got the molasses like crud for a while, then intermittently with clean gas, and then clean gas the last few minutes. If I'm lucky, maybe most of it is gone.
 
Ya the tank I am showing is definitely a bad case example, and I knew it was much worse than yours but wanted to show some idea of what can exist. Surprisingly the engine still ran fairly well despite all the crud, the completely blocked return line nipple, and the encrusted screen on the pickup line. Actually how you described your tank is very much like the other one was in my other X.

Sounds like you were able to get it pretty clean with your method. I think perhaps the thing that might have let you down was the cleaning agent you used wasn't strong enough to fully remove the varnish. Perhaps it softened some of it, which is why you are finding it in the fuel supply after the cleaning.

Let us know what you find, but for me removing the tank seems much easier than trying to do it in the car. I find that I wrestle with it a lot to get all of the insides well cleaned. Something came up this morning that will prevent me from working on mine for a couple days. But I will report back after the acid treatment.
 
Dr.Jeff said:
Ya the tank I am showing is definitely a bad case example, and I knew it was much worse than yours but wanted to show some idea of what can exist. Surprisingly the engine still ran fairly well despite all the crud, the completely blocked return line nipple, and the encrusted screen on the pickup line. Actually how you described your tank is very much like the other one was in my other X.

Sounds like you were able to get it pretty clean with your method. I think perhaps the thing that might have let you down was the cleaning agent you used wasn't strong enough to fully remove the varnish. Perhaps it softened some of it, which is why you are finding it in the fuel supply after the cleaning.

Let us know what you find, but for me removing the tank seems much easier than trying to do it in the car. I find that I wrestle with it a lot to get all of the insides well cleaned. Something came up this morning that will prevent me from working on mine for a couple days. But I will report back after the acid treatment.
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I'm pretty sure the detergent I used had no effect on the varnish. It was stuck well enough that it survived the pressure wash. I'm pretty sure it was the fresh gas that dissolved it after being in there for about a week. It was interesting that the fuel system behaved normally up to that point. The car was probably started a dozen times or so for tuning and was running long enough several times to warm up the cooling system. Both fuel filters were completely clear up to this point. Then, over the course of less than 48 hours, I go to start it up and nothing fires. I open the engine compartment cover and both filters were completely dirty from just cranking the motor for that short time. I should note that the pre filter, a 90s era Fram, was much less effective than the new Wix post filter, which saved the carbs from receiving this junk.
 
Filter elements come in all different grades of filtration (micron size). I saw a chart somewhere online with the specs for a whole bunch of filters and the spread of filtration range was surprising. Even for filters from the same maker but for different vehicles. Unfortunately they don't specify the rating on the filter and the data is difficult to track down, if the maker offers it at all. However I have seen some aftermarket "universal" type filters made for performance applications where they offered a choice of elements with different micron ratings (the finer the filtration the less flow it allows). I suppose the discoloration might not have been actual 'particles' as we think of them, but very fine molecules that do not harm anything (eg. 'stain').
 
Interestingly enough, both of the filters were specified by the manufacturer for the 1974 X1/9 application. It would appear that WIX has a higher expectation in 2018 for the application than Fram did in the early 90s. I bought the Fram filter a few weeks before the engine blew up in 1995 and never got a chance to install it until now. I went to O'Reilly's today to get two WIX 33001 filters but they only had one left. I'll pick up another one tomorrow as I'll be near a location that has plenty. I'm not sure it is the best filter for the application but at least I know it is good enough to protect the carbs. I originally picked it because it was the only compatible filter that even listed its filtration rating - 12 microns. The smallest orifice in the carb (ignoring the intake screen) is 450 microns (pump jet) so hopefully it is sufficient.
 
My '84 had molasses in the tank from sitting for years. I drained what I could then half filled with E85 and let it sit (with some agitation). I drained and then repeated a couple of times. Once I filled with real gas it went through a few pre filters but the high percentage of ethenol did clean the tank without having to remove.
 
I wonder if that old filter from '95, after sitting on your shelf all those years caused the element dry out and crack? That would allow a lot of junk to pass through it.
I once had one of the large Bosch fuel injection type "can" filters come apart internally. Tiny bits of filter media (plus all the dirt, etc) went through the whole system and clogged the injectors, etc. - huge mess. I've never lived where E85 was sold so that would not have been a factor, but it will destroy most fuel systems not specifically made for it.
 
twincam69 said:
My '84 had molasses in the tank from sitting for years. I drained what I could then half filled with E85 and let it sit (with some agitation). I drained and then repeated a couple of times. Once I filled with real gas it went through a few pre filters but the high percentage of ethenol did clean the tank without having to remove.
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Sounds similar to what I may be dealing with. Letting regular gas sit for about a week seems to have put the stuff into solution. I'd consider cleaning it with E85 or regular gas but I've found that gasoline is rather difficult to get rid of. Most of the places that take old oil around here won't take it.
 
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