On 9/27/2013, Jim Cheatham in Amelia, VA wrote:
"What should I do to make sure there isn't any dirt or loose rust in the tank before I install it? One person told me to put water in it. I'm not sold on that idea. I'm wondering if I should put some gas in it and slosh it around and pour it out. Anyone have any suggestions"?

I would rinse it out with petrol, save the draining in a clean pan, and see if any sediment comes out with the fuel. Keep rinsing until it comes out clean. I mean really clean so you can strain it through cheese cloth or a paint filter and find nothing.

Then Jim Cheatham wrote:
"Do you think I should use the drain plug on the bottom of the tank to remove the fuel I put in the tank for cleaning it, or just pour it out of the fill spout"?

The drain plug should do a better job of getting the fuel out, as that port is flush inside. I'm pretty sure the filler pipe goes through a bit to the inside where the end of the tube makes a bit of a dam when inverted that would keep some fuel inside, and also prevent the dirt from flowing out.

I did this once for a Mustang around 1979. What came out after filtering was about half a teaspoon full of very fine rust dust. That was enough to sometimes clog up the fine mesh filter sock on the pickup tube. I think the MG fuel tank has no pickup filter inside, just an open ended tube. But you never know what might get inside the tank, like tree leaves, or a bit or errant sealant someone may have used on the sender unit gasket. If the tank was coated internally in a past life, that coating may be dissolved by modern fuel with alcohol content.

If cleaning the fuel tanks does not solve a dirty fuel problem, then you can take the tank to a radiator shop to have it boiled out for best internal cleaning. Coating the inside of the tank afterward is optional, and is the subject of another tech article FU-100A.