M1Mustang69 wrote:

I asked if there was a product to clean it. Of course new is ideal but this person does not want to spend the money, clearly, so new is not the obvious answer, like it would be for most of us obviously.

Let's stick to answering the questions asked

Well then captain obvious, go ahead and give CLR a try and report back with your results. What's obvious is your friends experience with mustang fuel tank issues wouldn't fill up a thimble.

Josh is right.  Put a new tank in it or you will be chasing this kind of crap forever. 

Or, remove the tank. Throw a three foot long piece of 1/4” steel chain in there with some Dawn and water.  Stand there for twenty minutes shaking the tank so the chain slides around the interior surface, scouring the inside of the tank. Rinse and repeat, then do a final rinse.
Reinstall the tank.  Fill tank 1/2 full.  Note gas coming from any pinholes in the tank.  Buy a new tank.

LMAO MS....

well said Don....

I was talking to my father in law yesterday about a project one of his friends is starting.  Ironically it has a fuel tank that is impossible to get, so his technique is to use muriatic acid to clean the tank, then go to a 50/50 solution of acid and water (always pour acid into water not the other way around, my contribution from chemistry class), and then thoroughly rinse several times.  Were I forced to reuse a tank this is what I would do.  Make sure to wear proper protective gear (heavy gloves, respirator, etc).  Again though, I don't think the expense of the chemicals and protective gear is worth it given the cost of a new tank, nor the risk. 

If'n I was in his socks I would consider posts 20 and 21. Get a new gasket, remove the sending unit and look at the inside with a flashlight and mirror. Then you will know which direction to go next. I have no experience with CLR. If there is rust in the tank you are sunk. There used to be "Sloshing Compound" available in the old days but I think it has been outlawed for good obvious reasons.

We're in Canada.  And let's be mindful of people's financial situations.  Fundamentally we do not know what anyone is going through. $200CAN or more with a sending unit maybe out of reach for some.
Plus he doesn't turn any wrenches so now there's labour.

It's not a hobby for him, he's owned the car for 40yrs

As I mentioned earlier, cleaning an old gas tank can result in pinhole leaks when the rust is cleaned away. 

Doing this is not only financially foolish, but can be very dangerous.

What is the first thing one does when they clean out and reinstall that old tank?   They go fill it up with gas. 

Since most of those pinholes are under the top of the tank due to prior condensation issues, gas sloshes up through the holes and gets the trunk mat saturated or fills up the valley around the tank perimeter.  Or, they park it in the garage and don’t notice the gas leaking on the floor as they sleep.   Ever wonder why gas water heaters in the garage are always mounted up off the floor?

My whole point is:   It is not worth it to deal with a tank that has problems. Dangerous, as well as the junk continually flaking off the inside will cause untold carb problems for now on.

Like TKO explained, those who refuse to do things like this in a proper fashion shoukd just learn to do it themselves. 

Been there, done stupid stuff when I was young and broke, and learned from it.  The hard way.  Like I always say... I didn’t learn all this crap by doing it right the first time.

M1Mustang69 wrote:

We're in Canada.  And let's be mindful of people's financial situations.  Fundamentally we do not know what anyone is going through. $200CAN or more with a sending unit maybe out of reach for some.
Plus he doesn't turn any wrenches so now there's labour.

It's not a hobby for him, he's owned the car for 40yrs

 
The last time I checked some early Mustang gas tanks were made in Canada and that Canadian Tire could get them at a reasonable price. As for the sender, might be some good Used ones floating around out there at a good price. Might be worth a try.