Light fuel tank rust solutions?

[Cherryriver]

I'm getting back to planning for the '86 I picked up at an estate sale a couple of years ago. It only has 6000 miles and is complete and cosmetically pretty decent.
The carbs, however, were atrocious and I haven't had much luck with going after them. Upon reassembly they were leaking gushers.
I know better, and will need to get back at them.
I know I'll be getting the fuel tank out, in order to replace the fuel line at the bottom exit. The original crumbled into almost dust when I went to disengage it.
I peered into the tank best I could and don't see any drastic flakes of rust, but the walls are pretty red.
I have seen plenty of methods but I'm willing to listen to any suggestions. It seems to me that getting the detritus out of there after a cleaning could be a problem given the shape of the tank.
I think the tank's salvageable- I've see a lot worse- but as long as it's loose I think I ought to do something.
Bill

[Van Voyager]

Evaporust is your friend.

If it's going to need more than just de-rusting, then the POR motorcycle tank kit is a good option (I've used it successfully in the past with great results - everything still looking good after more than 20 years).

At the risk of stating the obvious; you'd want to remove the sender assembly first.

[Nails]

And while removing the sending unit, test it to see if the low fuel light comes on when above any fuel level. (Dunno if '86 had this.) These commonly die, but you'd never know until it's too late. Cheap and easy repair. Check Dollar4Dollar, or search here for "Mustang".

[triton28]

https://secure.cougarpartscatalog.com/fm-ef008a.html

[Nails]

https://secure.cougarpartscatalog.com/fm-ef008a.html

I picked one up for less than that at the local NAPA store. They pulled it right off the shelf -- I just brought in a part number that I found here.

[VoyKimmer]

What is the part number that you got it from NAPA ?

[Nails]

For heaven's sake, I can't remember whether I took my pills yet today.

I found this alternate part on here somewhere, but I can't find it again now. Maybe I just asked NAPA for a low-fuel sensor for a 1967-1973 Mustang or Cougar, as Dave mentioned here (viewtopic.php?p=92707#p92707). It should look exactly like OEM; and then it'll perform exactly like OEM.

[Sci_]

How to remove rust in a motorcycle gas tank.
I had bought a 2001 Kawasaki Voyager XII that had sat in a garage for 8 years and the gas tank was plum full of rust. I researched hours and hours before I came up with the best way to handle the rust.
First off, vacuum tank, inspect with 7 watt Xmas tree lamp and small swivel mirror. Power wash, inspect. If it’s real rusty, use the nuts and bolts trick or a chain to get rid of the bulk of the rust flakes. I took turns shaking the hell out of mine with my sons taking turns (I didn’t have a dirt bike to strap it to and take it out for a rough ride to bounce the crap out of it).
Put a 50/50 mix of phosphoric acid & water in the tank and seal it up good (it will ruin paint). Swish around, rotate occasionally and let work for about 8 hrs. Always add ACID TO WATER-NEVER add Water to Acid.
Empty tank. Rinse with water and then fill it with a solution of water and a ½ box of baking soda to neutralize the acid. After 15 minutes, rinse the tank again with water.
Immediately rinse with ½ gal gas with an once of Heat.
Next rinse with pre-mix gas (25:1, gas to 2 cycle oil), swish around.

Notes:
-TSC sells slightly diluted phosphoric acid by the gallon. Cheap. Whatever you buy, make sure it has phosphoric acid in it, and not sulphuric acid or something else like that.
-Phosphoric acid converts rust to iron oxide that is rust resistant.
-You can dilute the discarded Phosphoric acid again and put it in your garden.

[GrandpaDenny]

-Phosphoric acid converts rust to iron oxide that is rust resistant.

Huh? Rust *IS* iron oxide.

[Sci_]

-Phosphoric acid converts rust to iron oxide that is rust resistant.

Huh? Rust *IS* iron oxide.

Good catch. My bad. I should have said phosphoric acid converts iron oxide (rust) into a layer of iron phosphate which then acts as a protective coating.
Sorry about that,
Sci

[GrandpaDenny]

-Phosphoric acid converts rust to iron oxide that is rust resistant.

Huh? Rust *IS* iron oxide.

Good catch. My bad. I should have said phosphoric acid converts iron oxide (rust) into a layer of iron phosphate which then acts as a protective coating.
Sorry about that,
Sci

Oh, ok so is that what rust conversion solutions use? If so, will your tank turn black inside?

[Nails]

Oh, ok so is that what rust conversion solutions use? If so, will your tank turn black inside?

My take-home: The rust stuff I've used -- that turns rusted metal into a black, paintable substance -- is a gel, not something I'd want to slush around in the tank. And "by the gallon" sounds a lot cheaper.

I've never looked up this chemistry. But I did notice a warning that using it on steel that isn't actually rusted can cause rust. Maybe the careful rinses take care of that. (At the time, I was working on the inside of doors that had "cancer" along the bottom.)