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Discussion Starter #1 (Edited)
There's a couple of us interested in an aux fuel tank, so I figured it was time for a thread.

In my previous tow vehicle, previous meaning up until 26hrs ago, I had a 28gal fuel tank in the bed. I really liked the range the extra fuel gave me. That allowed me to be choosy about where I planned to refuel. I could hit a truck stop that had lots of room for my trailer and had good prices. Not to mention, if I could restrain my fluid intake I could get to events 6-8hrs away w/o stopping and therefore make really good time.

State laws differ on aux fuel tanks. In GA for diesel you can use gravity feed, which means no pump and no gauge needed. If you need to use a pump then you also need to have a gauge or you will run the aux tank dry and your pump will burn out.

This is a common gravity feed solution. RDS Diesel Install Kit for Auxiliary Diesel Fuel Tank — Fits Chevy/GMC Trucks 1999 - 2010, Model# 011029 | Auxiliary, Transfer Skid Tank Accessories| Northern Tool + Equipment
You plumb it into the fuel filler hose and a check valve keeps it from overflowing out your cap. Works well, altho our capless design does have me a little concerned.

Today, while I was installing airbags, I took a look at our fuel filler hose. I was concerned that it might be unconventional because of the DEF port. I can now say that our fuel filler hose looks entirely conventional so plumbing in the above kit should be easy.

Picking an aux tank. I have a shortbed so bed space is precious and I have a tonneau cover so I've only about 17" of available height. Between tongue weight and putting some stuff in the bed I'm going to be knocking on the truck's capacity so there's no sense trying to carry 250lbs of diesel. For a couple months I prowled around for ideas on something more modest then the old 28gal tank. Maybe something half that size. And maybe something I could easily remove if I needed the whole bed to carry something.

What I ended up getting is a 12gal plastic fuel tank. The kind of thing a person would probably use in a boat. I'm going to put a quick-disconnect in the fuel line so I can easily remove it. It's not the most rugged thing, but it's sitting on a bed mat so it won't get chafed and I'll strap it down securely. Since it only holds 12gal, it will spend a lot of it's life empty so it shouldn't be under much stress.
 

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That's actually a really good idea! Well done... I don't think it will be long before titan or one of those companies come out with a tank that gives us an extra 10-15 gallons....probably closer to the 10 judging from what I saw when I looked under there tonight
 

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Discussion Starter #3 (Edited)

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"If I could restrain my fluid intake"... How true, how true. I could get there driving as fast as someone going to the airport, waiting, flying and waiting some more. It would put short flights out of business all because of a ...

There are many plastic tanks around. You could even use a plastic can. I had a 30 gallon in-bed tank on my 2500 Cummins for over 10 years. It was a PIA.

None of them have a built-in fuel outlet at the bottom. That means they either have to be pumped, primed and then siphoned or cut open for some kind of drain. Cutting a hole and fitting a drain is not easy because of the materials to properly and strongly fit the drain pipe in. My siphon method worked with a prime ball, like in outboards. Only thing is the primer bulb never held up due to diesel use. All I ever saw were made for gasoline and diesel messed them up. I would get about 2 years from each and then trouble. Moving around would also slosh the fuel and break the prime, ending the fill.

I would go metal. Even a metal fuel can would be better. With a metal can you could drill and tap the can lower point for an outlet tube. Do it from new and you can weld the darn thing on. without fumes causing problems.

Look at the RDS offerings for metal tanks. They have many styles and capacities. I like the 20 gallon model but there are smaller and larger. Most but not all, drain from the bottom and include a shutoff valve.

That check ball on the inlet line is nice to stop overfilling. Now YOU cut into the stock filler tube and see if that plastic inner liner tube is in there.
 

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Discussion Starter #5
That check ball on the inlet line is nice to stop overfilling. Now YOU cut into the stock filler tube and see if that plastic inner liner tube is in there.
I will. Just gotta have some free time. Yesterday I spend much of the day with the tonneau cover, fabbing brackets that the CL seller failed to provide. Painted it too.

Today was spent fooling with towing issues. Still isn't quite right but I'm getting there.
 

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In researching aux tanks and cheaper top box options for my motorcycle, I stumbled onto marine fuel tanks. Specially designed for diesel fuel, come with fittings in spots you choose, easy to plumb, etc. Just need to bolt that suckers down. They also tend to come in a variety of shapes and configurations to fit difference spaces on boats. Might be a solid alternative for an aux fuel tank project. Not the cheapest, mind you, but certainly up to the task and built for the job.

Geez, with an extra 10 - 15 gallons onboard, it's theoretically possible to exceed a thousand miles per fill-up. If you can't find fuel before then, you're trying to run out...LOL (At least in 'Merica...in Canada, it's doable, and not on purpose...)
 

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Ordered my tank today. Got word it will be "drop shipped" here from the manufacturer (RDS). Got it $40 cheaper than from Northern Tool. Had to get the fill kit from Northern Tool as JustTanks did not have the right kit.

Now to deal with the filler line and a possible cut into an inner pipe. Hope it's not an "oops"!

Right after that I found a leaking and defective transducer on one of my twin GPS/sonar units. Bummer. Ordered another today. It was as much as the whole tank and filler kit. Don't own a boat.
 
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Sitting on my loading bench. Came today. Fits right in front of the wheel well behind the operator side. RDS 20 gallon with three upper ports and a bottom drain, locking fuel cap and fuel gauge.

Ranger I think you ordered the wrong fill kit from RDS. There's a new one listed on Northern Tool that I now have on order. The fill hose and plumbing is a bit smaller than the older one you listed. It's on the Northern Tool site.
 

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Discussion Starter #9 (Edited)
CPT, can you post a link the part you mean?

Another charm of the aux tank is that you get all the capacity of the OEM tank. The top of diesel tanks always fill with foam. With an aux tank, once the foam settles down below, a couple gallons from the aux tank goes into the OEM tank. When you fill up before roadtrip, take along a diesel jug and fill it too. Then the next morning before you head out, top off the aux tank with the jug and off you go.

Later edit. I think I found the aux fuel kit you mean. Bummer. Well, I'll measure things carefully before I start cutting.
 

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RDS Diesel Installation Kit — Fits 2013 and Newer Dodge Diesel Passenger Trucks | Auxiliary, Transfer Skid Tank Accessories| Northern Tool + Equipment

I called RDS months back. We talked of the measurement of the filler hose. They confirmed this is the one you want.

Right now I'm awaiting it from Northern Tool.

One thing about that tank I got in. It is NOT as pictured in their ads. The one pictured did not have those two extra outlets that mine has. Not sure the keyed cap was in the picture either. Quality is super from what I can see. Those extra outlets, if they have drop pick-up tubes, mean you can use a syphon system with bulb if you wish.
 

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I'm looking for a tank that will fit side mount between the back of the cab and up and over the wheel well like some tool boxes I've seen.
I have the 6'4 bed I refuse to call a long bed. I want to keep full width ability. Now that I'm thinking about the aux. tank I'm glad I ordered the air suspension.
 

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That ATTA tank is expensive. Then you add another $300 for that push/fill. It is nice though.

One thing. I had a 30 gallon tank in my 2500 Cummins bed for over 10 years. Thought it was too big. It took up a lot of space. Of course, 30 gallons is a lot of fuel and I sure used mine. This truck should be easier on fuel.

FYI, the 20 gallon RDS I got was $260. Darn fill kit was over $90 shipped.
 

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Discussion Starter #15


Sitting on my loading bench. Came today. Fits right in front of the wheel well behind the operator side. RDS 20 gallon with three upper ports and a bottom drain, locking fuel cap and fuel gauge.

Ranger I think you ordered the wrong fill kit from RDS. There's a new one listed on Northern Tool that I now have on order. The fill hose and plumbing is a bit smaller than the older one you listed. It's on the Northern Tool site.
I think RDS says your tank, the 72587?, is 18" tall. Because of my tonneau, I have only ~18" of height so that's cutting it a little close. Your tank exactly 18" tall with the cap on?

How are you going to get to the aux tank's filler port since you have a cap on your truck?
 

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Discussion Starter #16 (Edited)
Almost finished the install of the aux tank today. Everything is done except for some "dry-break" connectors in the hose. Since I want my aux tank to be easily removable, I want an easy way to disconnect the hose.


Re. the aux fuel tank "kit." Recall on p1 Captainmal found that a new kit had just hit the market for our trucks and I'd bought the old kit. This still needs to be clarified. Captainmal described his adapter as smaller in dia. than my adapter. This had me worried when I started the install this morning. After measuring the outside dia. of the filler hose and the diameter of my "might be too large" adapter in the aux tank kit a couple times, I chose to drive on and hope for the best. After cutting the filler hose with a razor, what I found is that my adapter was not too large after all. In fact, I'd a rather it was slightly larger in dia. The filler port hose ends slipped over it so easily that I was a little concerned about how tight the seal would be. In the end I slathered the adapter with sealent goobage before putting it in place and tightening up the hose clamps.

The install went fine. The only thing that is not ideal is that the drain port that I created for the 12gal tank isn't all that strong. As long as I don't put any mechanical stress on it tho, I think it will be fine. I drilled a hole just big enough that a 1/2NPT adapter would cut threads into it. Then I slathered it with sealent goobage. Had I been better prepared I'd have scared up some kind of really serious epoxy. I tested the port for leaks and it's fine. Down the road, if I keep this 12gal container, I might redo that port with some epoxy.


I spent a fair amount of time imagineering how I was going to do the fastening points. The passenger side of the bed is pretty easy to get to but I was determined to put the aux tank on the driver's side of the bed. That will make it far easier to fill up at the gas station. I don't want to be standing in the bed of the pickup with the fuel hose draped across the truck. This would be sure to mar up the paint on the L fender.

The underside of the bed near the filler port is hard to get to. Ultimately I decided that I wasn't going to be able to just put hooks in the bottom of the bed and thread nuts on to them from below. I needed a solution that was self-anchoring that I could do from above.

So I did what I always do when I need a solution. I went to Home Depot.
Below is an eyebolt on a 1/4" shaft and a sheetrock anchoring device. It's plenty strong. I was able to get to the underside of one eyebolt so I fastened it down with a nut. The other 3 have these anchoring doohickies.


I have a rubber bed mat so I had to cut holes for the eyebolts and hose. The discoloration on the bed mat is from a rainstorm coming thru.
 

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How do I get to my tank??? Open the side window.

I always have caps built with a side window that opens up. The one I have now from ARS is called the "Outdoorsman" window. Open the window ... fill the tank.

Ranger. Your tank is plastic. Expect it to expand and contract with the heat and fumes. In some cases that expansion and contraction will be dramatic to the point of distortion. Watch the lower drain point for potential problems over time and those expansion cycles. My take is you should have done a simple pump bulb with the outlet at the top and let nature empty the tank. You can also expect some dramatic bleaching out of the tank by the sun and drying of the plastic. Of course, your cover over it will help with the sun but may exasperate the heat issue.

I had one plastic tank that was 30 gallons. I know. I know.

Would like to see a picture of where you put that "wrong" filler adapter. It was supposed to be vertical. Did you find room?
 

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Discussion Starter #18 (Edited)
How do I get to my tank??? Open the side window.

I always have caps built with a side window that opens up. The one I have now from ARS is called the "Outdoorsman" window. Open the window ... fill the tank.

Ranger. Your tank is plastic. Expect it to expand and contract with the heat and fumes. In some cases that expansion and contraction will be dramatic to the point of distortion. Watch the lower drain point for potential problems over time and those expansion cycles. My take is you should have done a simple pump bulb with the outlet at the top and let nature empty the tank. You can also expect some dramatic bleaching out of the tank by the sun and drying of the plastic. Of course, your cover over it will help with the sun but may exasperate the heat issue.

I had one plastic tank that was 30 gallons. I know. I know.

Would like to see a picture of where you put that "wrong" filler adapter. It was supposed to be vertical. Did you find room?
I've had several caps over the years, but never one with a side window that opened. Awesome.

The plastic tank has a vent at top. I just need to rig up a vent hose.

I hear you about the siphon hose, but I want this puppy to drain.

We're saying the same thing, back on p1, re. on the orientation of the adapter. I checked the instructions. The adapter is supposed to be as horiz as possible with the valve fitting at it's top. That puts the valve fitting as vertical as possible, necessary because the check-ball needs to float "up" to cut off fuel flow from above.

You never answered the question re. the height of your aux tank. I really like the idea that this one is easily removable, but there's other more robust tanks that have my eye. I worry about them fitting under my tonneau tho. My last 3 tow vehicles had caps. I want to try a tonneau instead for a while.
 

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Ranger. Send me a picture of your filler connection and I will go out and measure that height now.

RDS makes another model that's 18 gallons and is lower. I'm not sure it has a bottom drain as it's more horizontal looking and I wanted vertical.

Heck. I'll go outside right now and update this in a minute.

Took more than a minute....

Man tank is 18" high. Top of outlet tubes are 20". Top of cap is just over 21" Where you see it is not exactly where it will be. I just set it in there as my fill kit has not arrived.

Picture is from the rear a bit so you can see how high it is in relation to the bed. When installed it will be tucked in behind that wheel well. The filler tube is long and threaded the whole way. You could cut an inch off it and still have plenty of threads for the cap. That would mean approximately 20 " up would be the lowest it could go.

OOPS - forgot. It's sitting on a thick mat right now. My guess is 3/4".
 

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Discussion Starter #20
I didn't understand the part about me measuring my filler connection. I was just looking at your tank at the RDS website and it's reported height. Since I have only 18" of height under my tonneau, that's all I have to play with.

What I wouldn't mind having is some kind of tank that was thin and went across the width of the bed. 20 or 25gal maybe. The problem is that the long thin ones are too tall.

Another idea is that I could get one of those bed extenders that flip out over the tailgate. That would make my bed length less of an issue and a non-removable aux tank would be no big deal.
 
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