Modify OEM subtank to increase capacity?

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I know there are products out there that utilize the spare tire area for huge fuel capacity. I especially like the tank that BajaOverland created, but it's out of my budget. I already have the OEM subtank, so I started wondering if there might be a way to split it, add a few inches to its depth, and then weld the bottom right back on. This seems like basic welding shop work to me and you could add probably 8-10 gallons of capacity. I figure that's two jerry cans worth of fuel so it worth investigating. The mounting straps could then just be extended and since you're re-using the bottom half of the tank, the straps would function just like before.

The problem is, I don't really understand how gas tanks work too well. If you increase the capacity, will the transfer pump be able to draw all of the fuel? Will the overhead fuel gauge still be accurate? Other potential problems?
 
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For the type of stuff you guys do I think you would be better off trying to source a long ranger tank. However what you are suggesting I think would work. However I am not familiar with the workings or location on that transfer pump.
 
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Markus,

You would definitely have to lengthen the pickup tube. The subtank is pressed/stakewelded together at its mid section so whoever cuts it and welds it back together has some tedious work and some lengthy welds that have to be absolutely perfect. The other issue is that as weight increases, I would be concerned with the strap mountings. Though I feel good about how I staked my rivnuts, I am not sure they would hold a couple hundred pounds across a rough road. So that would need to be addressed. If you decide to do it, take lots of pics.

Jim
 
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Yeah, the weight was one of my primary concerns with those straps. I just see so much "wasted" space under there and would love to use it more efficiently. The tank that Baja Overland has is perfect for me except for the price tag. Anyway, thanks for the input.
 
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I know there are products out there that utilize the spare tire area for huge fuel capacity. I especially like the tank that BajaOverland created, but it's out of my budget. I already have the OEM subtank, so I started wondering if there might be a way to split it, add a few inches to its depth, and then weld the bottom right back on. This seems like basic welding shop work to me and you could add probably 8-10 gallons of capacity. I figure that's two jerry cans worth of fuel so it worth investigating. The mounting straps could then just be extended and since you're re-using the bottom half of the tank, the straps would function just like before.

The problem is, I don't really understand how gas tanks work too well. If you increase the capacity, will the transfer pump be able to draw all of the fuel? Will the overhead fuel gauge still be accurate? Other potential problems?

If I were you and had already installed a rear bumper tire carrier and all the OEM dual neck gas filler and related plumbing, I would sell the subtank and source a long ranger 120 ltr aux tank with a compatable OEM sender. That's more than twice what the OEM sub tank carry.

Of course elmariachi is the subtank guru here, and could enlight you more.:grinpimp:
 
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What size is your stock subtank? Do you know if your 80 was sold new in Calif? I presume you have had the existing setup smogged in Calif. Passing smog test in Calif is the major issue for any fuel tank mods. The cool stuff that others have done with fuel tanks may not be an option for those of us doomed to live under the watchful eye of the Dark Tower, aka: California Air Resources Board.

Are there any other denizens of Calif out there that have pulled off an auxiliary tank addition and lived to tell the tale?
 
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Look at any stock tanks from other vehicles.. Maybe a lower dollar racing fuel cell?

I have a 19 gallon subtank from a mid-70s ford pickup that I think is going to tuck up in there nicely. Inlet on the correct side and all.

Haven't gotten around to more then collectings parts at this point yet.
 
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What size is your stock subtank? Do you know if your 80 was sold new in Calif? I presume you have had the existing setup smogged in Calif. Passing smog test in Calif is the major issue for any fuel tank mods. The cool stuff that others have done with fuel tanks may not be an option for those of us doomed to live under the watchful eye of the Dark Tower, aka: California Air Resources Board.

Are there any other denizens of Calif out there that have pulled off an auxiliary tank addition and lived to tell the tale?
I passed CA smog in October. First place I took it to had issues with the dual filler neck because I don't have the restrictor plate. Second place passed it no prob. No smog place is even going to know that there is a second fuel tank or that the little knob at the filler neck is a slider for two filler tubes.
 
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If I were you and had already installed a rear bumper tire carrier and all the OEM dual neck gas filler and related plumbing, I would sell the subtank and source a long ranger 120 ltr aux tank with a compatable OEM sender. That's more than twice what the OEM sub tank carry.

Of course elmariachi is the subtank guru here, and could enlight you more.:grinpimp:
Yeah, Iactually considered selling the OEM subtank to get a higher capacity one. I don't know what it's worth though since I'd be keeping the sending unit and filler neck, etc. It would be just a tank.
 

Romer

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You can buy the sending unit from Cdan for $45. I even have a spare because I thought mine was bad.

If your selling the subtank and straps I am sure you would find a lot of interest. Hard to make it work without them.
 

Romer

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Any idea what the complete subtank (with sending unit) and straps would be worth?

Hard to say.

I bought mine on aussie ebay with the oem transfer pump for $168 shipped and it took me two months to get it. I would guess between $200 and $400

I also know that SOR sells the setup for $900. I thought that was too high and thats why I went the route I did.
 
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At $400 selling the OEM tank would be worth considering because then it's only another $300 to buy the BajaOverland tank plus $50 for a sending unit. The reason I'm hung up on this tank capacity is that I'm building the truck up for an around the world trip and really fell like I need more fuel range. I'm not intersted in carrying a bunch of jerry cans because I have the Maggiolina upstairs and thus the associated CG issues. Adding jerry cans only makes CG more of a problem while putting my heavy fuel under the chassis seems like the way to go. I think man a fre or someone was selling a high volume primary tank replacement at one time, but I don't think that's available anymore.
 
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At $400 selling the OEM tank would be worth considering because then it's only another $300 to buy the BajaOverland tank plus $50 for a sending unit. The reason I'm hung up on this tank capacity is that I'm building the truck up for an around the world trip and really fell like I need more fuel range. I'm not intersted in carrying a bunch of jerry cans because I have the Maggiolina upstairs and thus the associated CG issues. Adding jerry cans only makes CG more of a problem while putting my heavy fuel under the chassis seems like the way to go. I think man a fre or someone was selling a high volume primary tank replacement at one time, but I don't think that's available anymore.

You got already the rear Kaymar (I guess with the tire carrier) and the dual filling neck so you have almost all the hard job done (and a lot of $$$ spent).

Sell your subtank with straps (you have it in the States so this is a big selling plus) and get ASAP at least a 120 ltr tank because even mine which is way bigger has less overhang that the spare tire on the OEM support but it has received a couple of non serious dents. Since you are going to an expedition, carryng a roof tent and all kind of required stuff, your cruiser will be a bit heavy so I guess you will not drive through something like the Rubicon.

It doesn´t make any sense to spend in a bigger primary tank replacement because it is way deeper and if you already remove the OEM sub tank and tire carrier you will have a lot of space behind the rear axle.

A 120 ltr will sit way up and you will have plenty clearance and enough fuel range.

Just my .002 cent
 
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