Dual tank setup

[Ramdough]

Looking at a large truck setup with a 54 gallon tank and a 100 gallon tank.

I plan to have a transfer pump from the secondary tank to the primary to use to refuel as needed. The primary tank will feed directly to the motor.

Would you use the 100 as primary or the 54 as primary. I am leaning towards using the small one as primary and then transfer multiple times as needed.

Thoughts?


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[Chorky]

Curious, gas or diesel?

 

[Joe917]

What is the truck?
We have a single 450 l tank that gets us a range of 2000km( Mercedes 917AF)
I would personally use the larger tank as the main.

 

[Ramdough]

It is an M1083

Diesel

Vehicle comes with a stock 54 gallon...... adding 100 gallons more.


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[Joe917]

Yes the weight won't be an issue and at 8mpg you will need the extra range.

 

[1stDeuce]

The one thing to consider is not putting all your eggs in one basket. IIRC, the Pan American GMC from the late 80's had a 100 gallon tank in the bed in addition to the ~36 gallon tank on the truck. Worked great for a while, until a weld seam split and dumped 100 gallons of diesel on the ground. They made the rest of the trip on the stock tank without too much trouble.

I've run a 60 gallon aux tank in the back of my trucks. (Diesel) In the beginning, I gravity feed the main tank through the filler neck vent hose. This worked fine on trips, but you had to remember to shut off the valve if you stoped for more than a few hours, or it overflowed and left a puddle. After a few overflows, I put in a sender, switch and solenoid valve. This was awesome, since I could see how much was left, and there were no puddles. When I changed trucks, I needed it to be removable, so back to gravity.

I sold it several years ago, and I'm now planning to make a ~20 gallon aux tank that I can just put a solenoid valve on and dump into the main tank. This will keep it from overflowing, and is about as simple as it gets. If I wanted a bigger AUX tank, I would put a momentary button that starts the timer for 20 minutes or so. (Heated backlight timer works well, I'm told...) Run the main tank down, then just whack the timer and fill it back up. Repeat until the aux is empty. No overflowing, no need to stop and flip a manual valve.

 

[Chorky]

^^^ Agreed with the above. I currently have a 19 gal rear and mid ship tank. I plan on replacing the rear with a 40 gal, and the mid ship with a 30 gal. I also plan to add another 30 gal mid ship on the passenger side. Some say its a bad idea, i prefer to have the redundancy in case I hit a rock and a tank gets damaged and starts leaking. Although one can argue that the electric switch to swap tanks can go bad, its been working for 21 years, so I bet 2 new ones would last another 21 years. So maybe 2 50 gal tanks instead?

 

[Ramdough]

^^^ Agreed with the above. I currently have a 19 gal rear and mid ship tank. I plan on replacing the rear with a 40 gal, and the mid ship with a 30 gal. I also plan to add another 30 gal mid ship on the passenger side. Some say its a bad idea, i prefer to have the redundancy in case I hit a rock and a tank gets damaged and starts leaking. Although one can argue that the electric switch to swap tanks can go bad, its been working for 21 years, so I bet 2 new ones would last another 21 years. So maybe 2 50 gal tanks instead?

So you are suggesting having 3 tanks? I would have to search for two 50 gallons that fit where a single 100 would.


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[Chorky]

So you are suggesting having 3 tanks? I would have to search for two 50 gallons that fit where a single 100 would.


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Well that is my .02 and my personal plan. Redundancy for one, and also load leveling/equalizing for 2. A single 100gal tank would certainly work, and probably work fine.

But to answer your initial question, I actually would run the 100 gal as primary, and use the 54 gal as the primary aux tank (assuming you plan to use diesel heat and other appliances) and have the 54 also as a 'reserve' tank. Because likely you would go through 54 gal rather fast. And having to use the aux pump often would be annoying I think. Plus, by the time you used the 100 gal (if used as primary), you might put a good dent into the 54 gal (if used as primary for aux systems).

 

[Joe917]

As far as auxiliary systems, generator, Webasto etc they do not need an extra tank just their own tank connection that is shorter thean the engine feed. this ensures you always have fuel to move,

 

[Alloy]

The 100 could be built with a baffle to split it in 1/2 with an external crossover. Run as 1 tank unitl/if there's an issue.
Raise the pickup for gen/heater 2"-3"off the buttom so these do not pickup water dirt.

 

[Ramdough]

So, the reason I picked a 100 is that it was the largest used tank I could find that fits where I can make space. I looked into custom tanks, and they were unjustifiable in my opinion.

Now I am a leaning towards using the 100 for everything as primary with shortened pickup tubes for Aux. Then the 54 as purely back up.

Thoughts?


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[Joe917]

Bingo! Add a quality pre filter water separator and your done,

 

[Curtis in Texas]

My Hauler is a 2000 Dodge Ram Diesel and I have a 100 gallon tank in the bed that I transfer fuel from. I have it set up to transfer fuel from it to the main 36 gallon tank. I used a 15 minute house light timer to run the fuel pump. This way I know that at an 1/8 tank on the fuel gage will require a full 15 minutes to put the main tank back to almost full. I mounted the timer below the steering colum.

The best part is I can transfer the fuel and not have to remember to turn it off. It makes a loud click in the cab when it shut off so I can tell when it turns off too!

I have a water seperator and fuel filter between the pump and the main tank. I've found that when it takes more than 15 minutes to get a full reading on the gauge, my fuel filter is ready to be changed. I empty the water seperator when I do oil changes.

Oh and I use a drilled out plug to make an orfice in the line to maintain a constant flow rate . Found the right flow rate by experimintation.

And my input line is welded into the filler neck just below the fuel cap so I can see that it is actually pumping the right amount of flow by just taking the cap off and looking at the fuel flow rate while the transfer pump is running.



I also have an 86 Isuzu Diesel Trooper and it too has a second fuel tank. But get this, having dual tanks was an easy add on.

Isuzu used the same frames under their 4 WD Troopers and their 4WD Pickups.

The pickups mounted their spare tire behind the rear axle. So that meant their fuel tanks had to be mounted inboard the frame parallel to the driveshaft under the passengers side seat.

Those frames have mounting for both locations. The trooper has their fuel tank behind the rear axle where the spare tire is on the pickups.
So to get dual tanks in my Trooper I mounted a 17 gallon pickup tank in the pickups location and have the 26 gallon rear Trooper tank in it's normal location. The best part is I have a fuel transfer valve that also switched the fuel gauge readings so I can read the fuel amount in either tank by just flipping the tank selector switch on the dash.

And both tanks have factory skid plates under them!

To fill them I used a "Y" exhaust tube muffler tube mounted inverted under the gas filler neck and still fill in the normal Trooper fIll tube. I just turn the gas pump filler neck to shoot fuel left for the rear tank or to the right to hit the Pickup tank. The vents are also "Y"'ed. Works great.

Im thinking that some other manufaturers used the same frame setups for their Suburans/ Envoys and Pickups. You may be able to add in a second factory fuel tank if you do a little homework. A day at the Salvage yard will tell you a lot. It may just be a little matter of welding on the mounting bracket too.

I don't really like having fuel cans hanging off the rear of my vehicels where they can rupture in a rear end collision. I've seen what 5 gallons of fuel can to in a heart beat with just a little spark.
MAYbe this will gve you guys some ideas of how to do things a little different........

 

[Alloy]

So, the reason I picked a 100 is that it was the largest used tank I could find that fits where I can make space. I looked into custom tanks, and they were unjustifiable in my opinion.

Now I am a leaning towards using the 100 for everything as primary with shortened pickup tubes for Aux. Then the 54 as purely back up.

Thoughts?


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Make sure the tank is built to be mounted the way you want. Be a bad idea to hang a .100" aluminum in bed tank that has downhand welds.