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Fuel Tank Repair
How to repair a leaking, dented gas tank.
I could have purchased a new tank for $120 plus freight.
But I wanted to see if this tank could be repaired.
The repair took 6-8 hours.

First thing is clean the fuel out of the tank and flush it until all of the fumes are gone!

Here is the tank with dents and holes.

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This picture you can see where the factory seam weld was.

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Take a zip cut wheel and grind a grove just on the inside of the existing seam weld.
Only grind threw the top sheet metal on all four sides.
The sheet metal will turn blue as it thins out, Don't grind into the bottom sheet metal.

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Take a cold chisel to separate the top sheet metal.

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Pull the top and bottom apart.

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Here you can see the bottom lip.

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Here you can see the top lip, as well as all the rust that builds up and get in the fuel system.

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Straighten the top lip out with a dolley and hammer, so it will lay flat when you weld it back together.

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Blast the top and bottom pieces of the tank in and out.

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The pin holes are hard to see, using a flash light behind helps locate them.

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Do all your spot welding on the inside of the tank using a copper backing plate, this will save alot of grinding later.

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Grind of the weld penatration the pops threw the sheet metal.

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Dolley and hammer all the dents out.

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Fit the Halves together.
Use vise grips to keep the sheets tight for welding.
Start at one corner and work around all four sides.
This allows you to tweek the grove back into the same location.
Tack weld about every three inches.
Grind all the tacks smooth so the seal weld can pass over them nicely.

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Set the tank up on a 45 degree angle so the seam can be re-welded in a down hand position.

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When welding ensure that the puddle fuses the sheet metal on both sides of the zip cut grove.
Use a slight whipping motion with the arc, backing up about 1/8" this lets you fix the weld puddle if it you loose the sheet metal on one side.
Repeat this welding on all four sides.

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Here you can see the weld penatration on the back side of the seam.
Grind up any welds.

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Use a polymer fuel tank liner to seal the entire interor of the tank.
This prevents rust from forming inside the tank and getting into the fuel system.
Tape up the openings.

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Pour the polymer liner into the tank.

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Tape the last opening and slowly rotate the tank.
Use a flash light to see that the entire interior of the tank is coated.
Pour the excess polymer out of the tank.
Let dry for 24 hrs

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Paint the exterior of the tank with 2 coats of epoxy paint.
Reinstall the sending unit, vent plug and nozzle gasket.
Excellent work and great write up. I wouldn't and didn't have the courage to do this but it is good to know it can be done.

[Image: 36319488731_8f2a376549_z.jpg]
73 Mach 1 Mustang
89 Dodge Shadow ES
94 Jeep Wrangler

That is a lot of work!
very interesting, did you use a sealer on the indside after getting it welded back together?

<img src="http://www.7173mustangs.com/gallery/1_12_09_14_10_32_45.png" />

- Nik
That's cool. I've never seen anyone cut open a fuel tank. Lot's of rust!

[Image: 386_07_10_13_5_58_42.jpeg]
My Mustangs:
71 M-code Mach 1, Medium Blue/White Sport, 4R70W, 3L50, Factory Ram Air.
72 Q-code Mach 1, Pewter/Black Sport, 4-spd, 3L25.
65 Convertible, Britney Blue/White/White, more modified than original.
05 Convertible, Legend Lime/Tan/Tan, future classic??
Great write-up! Its great to save original parts like that if you have the time and know how, but if you had to pay for 6 hours of labor it probably more economical to buy one.

Mike AKA Ole Pony & Rare Pony

Our current Mustang garage/driveway
1973 Mustang Convert - Bought in 1974 - Still have it!
2004 Mach 1 Oxford White Auto, Bought Sept 06

[Image: 20180127_082009.jpg]

upload a photo on internet

Good job!
Nice write up & nice work to showcase your skills ..But 8 hours of my time @ say $50.00=$400.00 +$100.00 in materials =$500.00 I understand why you did it but I'd buy a new one for the $120.00 before investing that amount of time into a questionable part.

I think its great you have skills like that and the time to do the repair. My dad was great at stuff like that. I remember one time back in the 60's the fuel pump went out on our Pontiac late at night about 200 miles away from home. He cut a leather diaphragm out of my mothers shoe, replaced the diaphragm in the old fuel pump and got us home safe and sound. He ran that fuel pump for several more months before replacing it; of course my mother was not too happy about her shoes.

Anyway, great job!

Mike AKA Ole Pony & Rare Pony

Our current Mustang garage/driveway
1973 Mustang Convert - Bought in 1974 - Still have it!
2004 Mach 1 Oxford White Auto, Bought Sept 06

[Image: 20180127_082009.jpg]

upload a photo on internet


great post but Please people if you try this do make sure the FUMES are fully GONE. An exploding gas tank can kill you.


[Image: a58hgh.jpg]
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