Alright so I took off the gas tank to this 89 and the guy i bought it from left gas in there since 99 sooo there is a ton of crap gas and this black sludge in there and the fuel valve. What type of solvent or cleaner can i use to salvage the gas tank, and the gas cap is also stuck on by that i mean the key will go in smoothly but wont turn lay some idea on me please

 

i have a tank just like yours, fuel sat in it, pretty rusty inside, and the gas cap was stuck on.

i didn't have a key for my tank, i took it to a locksmith, but he was unable to turn the lock cause it was so nasty. i ended up drilling the key hole, and it popped right off. beware as gas caps and matching keys are hard to find.

i've cleaned out rusty car gas tanks using muratic acid and water. its also good to get some small chain, to shake around inside and knock any of the loose stuff off.
i'm worried about damaging the paint using muratic acid, so i havne't attempted it yet on my tank. you might look into CLR, it takes off Calcium Lime and Rust, and might be a little safer for the paint. there are also products that coat and seal the inside of the tank. but you still need to clean it out the best you can first.

 

The muratic acid will clean it right down to bare metal so be prepared to treat it with something like Kreem or similiar as soon as it's dry. If you don't it will start to rust back almost immediately. Muratic works great on rusty tanks. You really don't even need to put chain or bolts/nuts in the tank, it will eat the rust up just by itself. How you mix it with water depends on how soon you want job done. I've done it 50/50 and let it sit good 24 hours and all the rust was floating.

 

thanks guys lemme see what i can do.