Cut open and reweld fuel tank?

[ETI4K]

I am attempting to repair some "body damage" to the bottom of my fuel tank.

So far, I have tried hot glue techniques and weld-on pins for use with a puller.  I specifically avoided going with a typical dent puller requiring holes for obvious reasons.  So while pulling on the pins, I've managed to produce two good sized holes.  Annoyed, but not crushed, I can now do whatever I need to remove the dents - including opening up the tank  to permit some hammer and dolly work, as the pulling techniques were a bust.

My thought was I'd cut around the welded seam along the side of the tank and then across middle of the support strap recess.  That way the new weld line will not be visible once installed (try as I might, I cannot get a welded joint to look quite like the ones Trev does on his YT channel - Trev's Blog.  The guy is a wizard).

The tank has the slightest damage from surface rust in a couple small areas including a very small patch inside, so it is completely restorable.  I just can't bear the thought of using it being so beat up.  So I am looking for any advice, suggestions, etc. that anyone cares to share.  Thanks!

BTW, the tank hasn't been wet with fuel for more than 20 years.  Explosion potential is zero - tried and trusted.

[dutchzcarguy]

Please be careful with welding a tank.. ive done that but i filled it with coolant.. so it does not explode in your face..  Others have done it by blowing constant air into the tank then also there is no danger...they say..

Top tip? : I would make a small hole in the top of the tank and take the dent out with a piece of wood from the other (later on) invisable side of the tank! 😉 

Edited March 22, 2021 by dutchzcarguy

[ETI4K]

Certainly seems less invasive, doesn't it?  Also a great way to hide the welds.

Maybe even less likely to leak in case of a tiny pinhole - I plan to seal with POR afterwards.

[heyitsrama]

I’ve read multiple people say shove a load of dry ice into allow the carbon dioxide to displace any fumes inside the tank. This was after washing out the inside of the tank with water for a long time, and using some thing to evaporate moisture inside.

I want to add baffles in mine, too much sloshing on the track, the pickup sometimes ends up without fuel  and ruins the run.

[Pilgrim]

Seems like most of those responding missed the fact that the tank hasn't had gas in it for more than 20 years. 

[heyitsrama]

@Pilgrim yeah i read that part, but on my first day of welding class we took a safety class, the professor said, 'Dont weld gas tanks, no matter how long its been sitting, there's gonna be residual gas on the surfaces'.

[EuroDat]

I have welded three tanks in the past and never had any explosions etc.

My advice. You plan to POR it afterwards and that is what I did on all three tanks with a similar treatment.

The tanks needs to be cleaned before you coat it, if you do that first you will, 1. Clean and prep the inside of the tank, 2. Remove all fuel residue so you can cut it open without any danger to yourself. Just make sure the cleaning solution is water based.

My second piece of advies is to cut a section out of the top of the tank directly above the damaged area. Make it big enough so you can get good access to the areas needing work. A weld repair on the top side will not be visable later and less likely to leak if you have a pin hole.

 

[Patcon]

There is some bracketry inside the tank so you will need to avoid those pieces. I think if I were going to cut on the top side. I would make a fairly big access hole. Doesn't matter to me if I weld a 6" patch back in or a 12' patch. It's about the same difference...

[grannyknot]

Whoa, looks like a Mexican Pinata,  lots of tank restoration businesses cut the tank in half to do the necessary work,  I've done 2-3 tanks now with the POR15 kit and in every case there was more than enough left over to coat the entire outside of the tank as well.

You may not want that look but it's an option if you like,  with the POR15 kit you must follow the instructions to the letter, the steel has to be scrupulously clean, warm and dry.

[siteunseen]

Just to add to your research here's some good pics thanks to @240260280

https://www.atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

 

'77 efi though. Not sure what you have but maybe useful in some way?

 

[ETI4K]

8 hours ago, heyitsrama said:

@Pilgrim yeah i read that part, but on my first day of welding class we took a safety class, the professor said, 'Dont weld gas tanks, no matter how long its been sitting, there's gonna be residual gas on the surfaces'.

When I was in high school shop, we used to cut up old cars and then put them back together.  Our shop teacher made us run water through fuel tanks before cutting or welding near them.  So, a fuel tank exploded one day.  I looked up to see the guy's expression as he stood there with a cutting torch in hand and staring at a suddenly very fat fuel tank. 🤯🤯🤯🤯.  

Kinda priceless.

That said, I actually lit a torch and (without hesitation) inserted it into the fill pipe.  No explosions, no flames, hence my comment:

"Tried (the flame) and trusted (the results)"

Thank you all for the good advice!  I did lose a friend who was smoking a cigarette while he refilled the fuel tank on his lawnmower.  It didn't end well for him, and I fully respect the significant danger of lighting off fuel vapors.

 

[Namerow]

There are no 100% answers to this question.  Lots of anecdotal evidence, but no robust guidelines.  Statistical populations of three.  A classic example of 'YRMD' (your results may differ).  All I can say is that if it all goes wrong for you, your last thought will be, 'F__'. 

Your wife may have a different comment .