Cleaning solvents

I cleaned my tank first with water only to get the BIG chunks out and then followed that with a 50% muriatic acid solution and a few foot long lengths of chain in the tank to help loosen the debris, followed by water, and repeat.  Once I had everything out that I could get out with that method, I used the POR-15 fuel tank kit to clean and seal the tank.  The whole process really sucks and is back breaking, but it does work.

As for question #2, I used gasoline for years and years to clean parts and my hands are now super sensitive to chemicals.  I would use kerosene and wear chemical resistant gloves.  It is safer than gasoline due to the higher flash point.

New gas tank.  It costs about $150 and is a safety item, therefore exempt from the budget.

It's a humber, I doubt a stock replacement tank is readily available.

I'm in a similar boat with my current build.

I'm going to try the chain thing one more time, but there's baffles in mine. I may go with 100 5/16 nuts instead and just count them upon exit to make sure I get em all out.

I highly recommend you NOT just run it, though. Make every effort to get out what you can before relying solely on filters.

The new fuel regs look a bit daunting, especially the part about not dropping the cell down through the trunk. But we did it on the mini and more or less had to in order to have access for getting the refueling jugs into the trunk. Not sure what's going to happen at the first 2011 race tech with it. The stock mini tank is a firebomb, for sure. Same for the moke.

If it doesn't get clean enough for me, I think I'm just going to toss my FuelSafe fuel cell in the rear area temporarily. I need to check the rules and EvilJohnius about a couple things, though relating to cabin isolation.

That humber should be pretty easy to stick a non FIA cell in the trunk (cheaper) and isolate it from the passenger compartment. I'd think that would be safer than the stock one anyway.

Did yours have old gas in it? I posted free 5 gallons of old gas (aka varnish) on CL and some guy in an old chevy diesel truck came over and poured it straight in his truck. Save me the hassle of disposal and the lingering smell until I disposed of it.

OK, don't hold me in suspense.   What did you use?

So far, it looks like the best solutions involve removing the tank from the car.   I was hoping to avoid that since the tank actually has a drain plug!   One advantage I have is a 3-foot flexible borescope so I can inspect my progress.

Spank, I'm impressed that you managed to get someone to take away your old gas!   That was pure genius.   I have no idea how much old gas I've got, but I'll find out this weekend when I drain it.

If your main issue is rust, reverse electrolysis works amazingly well and is essentially effortless besides setting it all up.  Just change the consumable electrode a few times and you're good.  Electricity does the work for you. 

http://myweb.tiscali.co.uk/andyspatch/rust.htm as an example.

Search reverse electrolysis gas tank and you will find a bunch of stuff.  You probably have everything to do it.  Basically caustic soda or phosphate free detergent, a battery charger, water, and some consumable electrodes.

Dont forget, its raw metal when you are done and can rust easily, especially with ethanol (and water) in gas now.  I think phosphoric acid will leave zinc behind on the metal to help protect it.  I think thats what por uses as "metal prep."

Yup, the gas tank is the container.  Fill it up with the solution and you need to hang the consumable electrode (that the rust ends up on) through the fuel level sender hole.  Be careful it wont arc out.  The tank gets - and the rust collector gets +.  You might have to change the consumable electrode if theres a lot of rust.

I wonder if a electroplating place would zinc coat the inside and out of a cleaned gas tank?

This of course cleans the inside of the tank.  For the outside you need a kiddie pool or a plastic drum if it fits to submerge parts of the tank in until its rust free.  You can rotate it and do a section at a time.  Or setup a rotisserie to spin the tank in the kiddie pool.  Sounds perfectly reasonable...

Tide Coldwater formula, stuff works remarkably well on old grease & oil. Pour it on straight, hit it with your wife's toothbrush and let sit. Rinse and buy new toothbrush.

I've also used a length of chain and Tide to clean out the initial gunk in old tanks, followed by liberal doses of WD-40 and more rounds with the chain. Nothing a dozen spare fuel filters won't fix.

I've never tried ireverse electrolysis with any varnished rusty bits so i cant say for sure how it will work on the varnished parts.  But its a safe bet the varnish is on the rust and the electrons should be able to get at the rust.

I've also read MEK is good at dissolving varnish but never tried it.  I've never had a varnished tank i cared to save.