Aux fuel tank idea - Tell me why this won't work

[IdaSHO]

I'm looking to add an aux tank to my little truck. Do you happen to have dimensions of the CJ tank you used?

My notes... Approx. dimensions 23" x 16" x 10"

 

[Alloy]

So I have had this idea rolling around in my head for some time. Having some spare gas is a good idea, but I am not a fan of the RotoPax. Spending $150+ to carry an extra 2 gallons doesn’t rub my budget the right way. Jerry cans are a lot cheaper, but are still a bit awkward to strap down, find a place for, … So, I came up with this.



Bolt a 15 gallon tank into the bed of the truck. (10”d, 15”h, 23”l) Drain the fuel out the bottom to a solenoid valve. The other side of the solenoid valve goes to the fuel filler neck between the gas cap and the tank. When the main tank starts getting low, flip a switch, open the solenoid, and the fuel drains down into the main tank. You don’t have to get out of the truck. You don’t have to worry about spilling gas down the side of the truck trying to refuel. You don’t have to try and hold up a 5 gallon jerry can up with your bad shoulder.

When I fill up at the gas station now, I generally put between 16 and 18 gallons in. With a 15 gallon aux tank, if I wait till about that same point on the gas gauge, I can open the solenoid, and completely drain the aux tank without worry of the main over-filling. I picked making the connection in the fuel filler neck somewhere because I thought it might be a little easier to tap. And if I do screw something up while making the hole, the filler neck will be easier to replace than the whole tank.

Can someone tell me why this won’t work? I am a fan of the KISS theory of design (Keep It Simple, Stupid). This is about a simple as I can make it. Although the engineer in me has tried to make it much more complicated.
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I'd be surprise if you can find a gas tank that has a fitting on the bottom.

You could used a diesel tank that has a drain on the bottom but it's a bad idea to drain gasoline off the bottom of a tank.

 

[JMacs]

You could used a diesel tank that has a drain on the bottom but it's a bad idea to drain gasoline off the bottom of a tank.

Why would it be a bad idea to drain off the bottom of the tank? Pumps pull of the bottom of the tank.

 

[Dave in AZ]

Why would it be a bad idea to drain off the bottom of the tank? Pumps pull of the bottom of the tank.

Sediment. Pickup tube from top is always a few mm above bottom, leaves sediment. Hole in bottom doesn't. Also leaks potential from bottom hole vs top pickup.

 

[IdaSHO]

Safety is a large concern as well. Tear a line, or connection to bottom of tank and you have no control over the flow of fuel right to the ground. Having to pump fuel out of an approved fuel container is a massive safety improvement.

 

[ThundahBeagle]

I just can not believe that we no longer have the stock or optional factory dual fuel tanks and filler doors like on the OBS 70's and 80's Chevy and GMC c/k pickups. But there must still be old plans lying around somewhere, so you could fabricate something like that almost to a tee. Fuel gage goes down to 1/4...flip a cut-over rocker switch, and watch it climb back up to full.

 

[Pacific Northwest yetti]

I just can not believe that we no longer have the stock or optional factory dual fuel tanks and filler doors like on the OBS 70's and 80's Chevy and GMC c/k pickups. But there must still be old plans lying around somewhere, so you could fabricate something like that almost to a tee. Fuel gage goes down to 1/4...flip a cut-over rocker switch, and watch it climb back up to full.

As we see more fleets switch to gassers due to DEF problems. It would not surprise me.

 

[oldnslow]

I just can not believe that we no longer have the stock or optional factory dual fuel tanks and filler doors like on the OBS 70's and 80's Chevy and GMC c/k pickups. But there must still be old plans lying around somewhere, so you could fabricate something like that almost to a tee. Fuel gage goes down to 1/4...flip a cut-over rocker switch, and watch it climb back up to full.

Those weren't all that great. The tanks were small so 2 were needed to get anywhere. They were also located outside the frame and a side collision would often open them up for an insant fire.

Then when (not if) the switchover valve stuck, you were left with just the one small tank. I have some bad memories of my 87 Chevy...

 

[JMacs]

The more you know, the harder this gets. And that darn idea of being safe doesn't help. You can get a rectangular tank that will accept a "traditional" in-tank pump. But those pumps that they design for are $450. I am sure they would custom fit the opening for a standard Toyota pump ($220) for a small fee, ... Finding the right pump that will work with the standard rectangular pumps pick-up tubes isn't as easy as you would think either. Not all the in-line pumps will suck from the top of the tank.

Back to the idea of safety. Not having the auxiliary tank flow off the bottom of the tank, I get. But strapping a plastic tank to the side of your truck, where it can det side swiped, jerry cans on the back where they will get smashed in a rear-end collision. Are those any safer?

 

[IdaSHO]

There is a reason "portable" fuel tanks are limited to 5-gallons.

 

[JMacs]

First, thanks all for indulging me while I bounce ideas around. Thanks for all the thoughts, ideas, and concerns. As much fun as it is trying to create a cool solution that will work with a push of a button, it was getting a little too much both in terms of complications and as well as costs.

I think I've got it. Simple. Effective. Safe. Now, it won't work while driving down the road. But that's OK. If I can't stop for 5 minutes to take care of things, something has gone definitely wrong in my travels.



https://fueltankparts.com/products/22-gallon 24x12x18 aluminum tank

 

[ThundahBeagle]

Those weren't all that great. The tanks were small so 2 were needed to get anywhere. They were also located outside the frame and a side collision would often open them up for an insant fire.

Then when (not if) the switchover valve stuck, you were left with just the one small tank. I have some bad memories of my 87 Chevy...

Interesting. I guess I just never realized how small the individual tanks were. Thought they were each the standard size. And I never happened to experience the rocker switch failure, not that I doubt you.

As for being located outside the frame, it was proven that NBC television had mocked up those trucks and augmented the flame to produce a jarring video for tv. Then again, new ones are on the inside of the frame, so why couldn't a second one of similar size be located on the other side?

The tank on my 2014 GMC K1500 is only 24 - 25 gallons (oddly, my 1994 Chevy K1500 Blazer - think original Tahoe, but 2-door - had a 30 gallon tank). The allure of a 2nd tank, so I could lug around 50 Gallons and traverse 800 to 900 miles between fill-up calls to me

 

[Alloy]

First, thanks all for indulging me while I bounce ideas around. Thanks for all the thoughts, ideas, and concerns. As much fun as it is trying to create a cool solution that will work with a push of a button, it was getting a little too much both in terms of complications and as well as costs.

I think I've got it. Simple. Effective. Safe. Now, it won't work while driving down the road. But that's OK. If I can't stop for 5 minutes to take care of things, something has gone definitely wrong in my travels.

View attachment 838877

https://fueltankparts.com/products/22-gallon 24x12x18 aluminum tank

Nope. It only works for the 1st minute then you get bored/distracted and don't notice the main tank is full until there's fuel on the ground.

 

[Alloy]

The more you know, the harder this gets. And that darn idea of being safe doesn't help. You can get a rectangular tank that will accept a "traditional" in-tank pump. But those pumps that they design for are $450. I am sure they would custom fit the opening for a standard Toyota pump ($220) for a small fee, ... Finding the right pump that will work with the standard rectangular pumps pick-up tubes isn't as easy as you would think either. Not all the in-line pumps will suck from the top of the tank.

Back to the idea of safety. Not having the auxiliary tank flow off the bottom of the tank, I get. But strapping a plastic tank to the side of your truck, where it can det side swiped, jerry cans on the back where they will get smashed in a rear-end collision. Are those any safer?

Try a search for "Carter Fuel Pump" I've been using them for decades. Put it on a 12V digital timer so it will automatically shut off

 

[IdaSHO]

I simply transfer for the 15gal aux tank to 35gal main tank when main reaches 1/2 full.

Math is hard.

When the small cheap solid state pump starts clacking, aux tank is empty.