For the second time in two years, I've smacked the bottom of my diesel
tank and ended up with a leak that was stopped using the FLAPS PermaTex
brand Gas Tank Sealer.

I don't remember the exact name (and threw the package away) but you
can't miss it... it's a roll of black compound with a white center,
about four inches long and a half inch in diameter.

To use it, you cut off a small piece and knead it till it turns a
uniform gray and becomes soft. You stick it over the leak and flatten
it.

Both times I have sanded the spot first. the first time I used it I
drained my tank first so no diesel fuel was leaking out. This time I
didn't even do that as I had just filled up.

It's amazing that the stuff works with greasy diesel fuel streaming out
of the tank,  but it does.

Highly recommended repair kit addition.

Jim