Okay, I decided to pull the tank out! Good thing I did because someone painted the tank without a primer coat. Every place where the paint didn't stick and water got behind the paint, there was a pitting and rust (oxidation).
The issue began as a leak in the rear of the tank. Three little pin holes in a weld. Apparently one of the previous owners attempted to use a putty sealer to stop the leak. I don't like tank sealers!!!!! Sure enough, the leak was behind the sealer.
Next Steps:
1) Strip the tank down to bare metal - DONE
2) Check for leaks - DONE
3) Do final cleaning of tank to assure it will be safe to weld.
Note: This is not my first time to weld a tank. My dad taught me how!
4) Weld the 3 inches!
5) Final sanding and prep for painting
6) PRIME THE TANK!!!!!!!!!!
7) Paint the tank.
8) Reinstall the tank.
9) Prey that my Cummins 5.9 Diesel will start without priming issues!
Got to decide which primer to use. Definitely one that etches!
The attached picture shows the fuel tank with some of the rust. The paint just peeled off where the rust was. The shinny parts are where the paint stuck, so I had to grind it off!