7.3 Gas Auxiliary Bed Tank Install

MiTremor906

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Location
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2022 AMB F250 7.3 Lariat
Well boys and girls, the time has finally come to reveal an alternative to the Transfer Flow 58 gallon tank for the 7.3L people. @Modman and I have been coordinating on this install for a while now and both have finally got them installed and hooked up.

Quick details between the two:
Transfer Flow Tank
58 Gallons Total​
Slight loss of ground clearance​
~$3,000 for tank​
ATI Auxiliary Tank
Additional 43 gallons (77 total gallons)​
Loss of ~12" of bed space (we both have said this is basically going back to an 1/2 ton short bed)​
~$1,600 (tank was $1,300 but tried to add in everything else I bought, might have missed a couple things)​

We took the ATI AUX43R tank and had it slightly modified so that we could attach it using the tie downs on the front of the bed, rather then drilling through the floor of the bed. Below is a model that shows the modification to the back of the tank, we left it slightly long to then trim it to the right width for our trucks and then drilled the holes to match the tie down bolt holes. We both ended getting the same fuel pump, Carter P4070, and mounted it directly to the side of the bed using rivet nuts. We then used bulk head barbed fittings to pass through the side of the bed down to the filler neck. We each purchased a new fuel filler neck so that we could route the tank directly into the filler neck but not ruin the one that came with our trucks. With this we removed the rubber lines that came with them and drilled and tapped the filler neck line for 1/4 NPT elbow. After it was threaded in and oriented the way we needed them (toward the rear of the truck) we also added a layer of JB quick weld for a second layer for protect. We did a few leak checks before this with water and didn't see any leaking so that JB weld is likely not needed but we both felt better using it. After that I designed and had 3d printed a couple of gauge pods to fit down on the side of the center console. We had slightly different gauges but both worked in the gauge pod. We did our wiring slightly different based on Modman already having power in his bed for his fridge, but both ended up with a momentary pushbutton on the left side of the steering wheel that starts a timed relay to let the pump run for a given amount of time (11 minutes for myself, which fills just a little more than a 1/4 tank and about 6 minutes for Modman that gets about 5 gals). We used Aux 5 to provide the main power to the gauge and momentary switch, when the momentary switch is pushed the led ring on it will light up only while power is being fed to the fuel pump as a visual indicator that the system is running.

We both have just recently finished up the project, so we don't have a ton of time using them but thus far we have no engine codes. I have used mine at least twice while driving, which was one requirement I had for this project, and have had no issues. Between all of the other road noise and radio, I can't hear the fuel pump at all. One weird thing I have noticed is that while driving the fuel gauge for the aux tank will go down normally over the 11 minutes it is running but the truck tank doesn't seem to move at all until after the 11 minutes and then slowly climbs over another ~10 minutes.

Parts/pieces:
Here is a data dump of photos, I started to put them in line with the text but it made it very chopping. There is probably plenty that I have skipped, or didn't clearly write out, and we have a ton more data in a private chat that can be pulled into here as people need/want.

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Well boys and girls, the time has finally come to reveal an alternative to the Transfer Flow 58 gallon tank for the 7.3L people. @Modman and I have been coordinating on this install for a while now and both have finally got them installed and hooked up.

Quick details between the two:
Transfer Flow Tank
58 Gallons Total​
Slight loss of ground clearance​
~$3,000 for tank​
ATI Auxiliary Tank
Additional 43 gallons (77 total gallons)​
Loss of ~12" of bed space (we both have said this is basically going back to an 1/2 ton short bed)​
~$1,600 (tank was $1,300 but tried to add in everything else I bought, might have missed a couple things)​

We took the ATI AUX43R tank and had it slightly modified so that we could attach it using the tie downs on the front of the bed, rather then drilling through the floor of the bed. Below is a model that shows the modification to the back of the tank, we left it slightly long to then trim it to the right width for our trucks and then drilled the holes to match the tie down bolt holes. We both ended getting the same fuel pump, Carter P4070, and mounted it directly to the side of the bed using rivet nuts. We then used bulk head barbed fittings to pass through the side of the bed down to the filler neck. We each purchased a new fuel filler neck so that we could route the tank directly into the filler neck but not ruin the one that came with our trucks. With this we removed the rubber lines that came with them and drilled and tapped the filler neck line for 1/4 NPT elbow. After it was threaded in and oriented the way we needed them (toward the rear of the truck) we also added a layer of JB quick weld for a second layer for protect. We did a few leak checks before this with water and didn't see any leaking so that JB weld is likely not needed but we both felt better using it. After that I designed and had 3d printed a couple of gauge pods to fit down on the side of the center console. We had slightly different gauges but both worked in the gauge pod. We did our wiring slightly different based on Modman already having power in his bed for his fridge, but both ended up with a momentary pushbutton on the left side of the steering wheel that starts a timed relay to let the pump run for a given amount of time (11 minutes for myself, which fills just a little more than a 1/4 tank and about 6 minutes for Modman that gets about 5 gals). We used Aux 5 to provide the main power to the gauge and momentary switch, when the momentary switch is pushed the led ring on it will light up only while power is being fed to the fuel pump as a visual indicator that the system is running.

We both have just recently finished up the project, so we don't have a ton of time using them but thus far we have no engine codes. I have used mine at least twice while driving, which was one requirement I had for this project, and have had no issues. Between all of the other road noise and radio, I can't hear the fuel pump at all. One weird thing I have noticed is that while driving the fuel gauge for the aux tank will go down normally over the 11 minutes it is running but the truck tank doesn't seem to move at all until after the 11 minutes and then slowly climbs over another ~10 minutes.

Parts/pieces:
Here is a data dump of photos, I started to put them in line with the text but it made it very chopping. There is probably plenty that I have skipped, or didn't clearly write out, and we have a ton more data in a private chat that can be pulled into here as people need/want.

View attachment 156183View attachment 156184
View attachment 156185
View attachment 156196

View attachment 156202View attachment 156204

View attachment 156203View attachment 156210View attachment 156208View attachment 156209View attachment 156207View attachment 156213View attachment 156214
Extremely detailed and illustrated install. Now I am 100% a 6.7 man, BUT, if I had a 7.3 this is exactly how I would have done it. Well done gentlemen!!
 
Very nice install. I dig the time relay/momentary switch setup as well as the bulkhead. Extremely clean setup. Thanks for sharing p/n and links.

I'm not terribly familiar with tapping into the filler neck on gas vehicles. You installed two fittings. One for the fuel to get into your fuel tank. Is the other one a breather?
below is a screenshot of one of your photos. What is going on underneath that ziptie? Why is it covered but the other isnt?

1715659053039.png
 
Very nice install. I dig the time relay/momentary switch setup as well as the bulkhead. Extremely clean setup. Thanks for sharing p/n and links.

I'm not terribly familiar with tapping into the filler neck on gas vehicles. You installed two fittings. One for the fuel to get into your fuel tank. Is the other one a breather?
below is a screenshot of one of your photos. What is going on underneath that ziptie? Why is it covered but the other isnt?

View attachment 156234
The other one is the vent line to let air back into the aux tank and theoretically if you overfill it, it can flow back into the aux tank.

The zipties just hold a sleeving over the fuel line to help reduce wear on it. You could add one to both but because the other one is a vent it shouldn't ever see fuel in it so we were just less worried on that one.

Here is the simple drawing from ATI on how to install it:
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Awesome write up! Been thinking about doing this to mine for some time now.
I wanted to do but could only find one other person that did it and their install didn't have a ton of details. If you do it and have any questions just let us know.
 
This was a pretty ambitious undertaking. It came out very clean and very user friendly. Thanks for sharing such thorough details.

I already have the TF tank for my truck but this would have been a serious contender for an upgrade option. I like that you kept it as minimally invasive as possible and completely reversible.

Any thoughts on the issue of filling the tank for those with a cap/shell on the bed of the truck? Obviously this would be a requirement for those with.
Well done guys!👍🍻
 
Last edited:
modified so that we could attach it using the tie downs on the front of the bed
FYI - You can see in the pictures but Ill just add that we are using the bolt holes for the tie downs to mount the tank.
We each purchased a new fuel filler neck so that we could route the tank directly into the filler neck but not ruin the one that came with our trucks.
This isn't a requirement, as @MiTremor906 stated, so the final cost could be reduced significantly if someone wanted to simply modify their OEM filler. We played around with alternatives quite a bit and having the filler in hand helped to visualize how we wanted to package the final routings...

Great summary @MiTremor906 ! I'll add some pics of where I had some unique items - bed wiring, switch, etc later today. We also accrued 25 pages of Private Messages as we bounced ideas off one another and fine tuned the solution. It was a true collaboration!
 
This was a pretty ambitious undertaking. It came out very clean and very user friendly. Thanks for sharing such thorough details.

I already have the TF tank for my truck but this would have been a serious contender for an upgrade option. I like that you kept it as minimally invasive as possible and completely reversible.

Any thoughts on the issue of filling the tank for those with a cap/shell on the bed of the truck? Obviously this would be a requirement for those with.
Well done guys!👍🍻
Probably another filler mounted from the shell into the aux tank would work. I was thinking the same thing 👍🏼
 
What is going on underneath that ziptie? Why is it covered but the other isnt?
That is from my truck. Adding to the comments from @MiTremor906 - there is a pinch flange close by and I wanted to ensure there was no long-term damage from vibratory movement over time.
 
Any thoughts on the issue of filling the tank for those with a cap/shell on the bed of the truck? Obviously this would be a requirement for those with.
Well done guys!👍🍻
I was thinking something along the lines of what Blade stated. If the cap had a window on the side you could probably just extend the filled neck up to the window to help give it a clean look.
Probably another filler mounted from the shell into the aux tank would work. I was thinking the same thing 👍🏼

I already have the TF tank for my truck but this would have been a serious contender for an upgrade option.
If you really want to be king of fuel you could add this to your TF and have 101 gallons of capacity. Imagine that fuel bill, hope you find somewhere cheap.
 
Nice clean install! I would rather give up 5/8" of ground clearance than 12" of bed space but to each there own.
Any concerns with liability since this design has not been approved by any state DOT?
 
The other one is the vent line to let air back into the aux tank and theoretically if you overfill it, it can flow back into the aux tank.

The zipties just hold a sleeving over the fuel line to help reduce wear on it. You could add one to both but because the other one is a vent it shouldn't ever see fuel in it so we were just less worried on that one.

Here is the simple drawing from ATI on how to install it:
View attachment 156242
Thanks for the clarification and a visual at that!

FYI - You can see in the pictures but Ill just add that we are using the bolt holes for the tie downs to mount the tank.
Excellent idea, btw. I would be completely shocked if this thread doesnt give someone else the idea of using those tie-down bolts to mount something.

Not surprising at all but... your tanks and the modifications are black. Did yall have the tanks spray lined or powdercoated? Looking at the photo it does not appear at all that yall ground it down, welded the ears and then rattle canned it (that approach isnt commensurate with this level of install anyway).

Thanks for sharing and for letting me ping yall with questions.
 
Nice clean install! I would rather give up 5/8" of ground clearance than 12" of bed space but to each there own.
Agreed on to each their own. I also couldn't stomach spending $3k to get 24 more gallons. That is why we found a way to get 43 more gallons and spend less then $2k. I also like the idea of having different options. If the TF was cheaper, I likely would have never gone down this route.

Any concerns with liability since this design has not been approved by any state DOT?
Here are a couple statements from ATIs website.

"Our Fuel Tanks meet the DOT requirements for auxiliary fuel tanks."

"Our aluminum auxiliary fuel tanks for gas are built to meet and exceed Title 49 CFR 393.65 for fuel tanks. The all aluminum .125” thick HD fuel tank was specifically designed for gasoline."

These are specifically design and intended for use with gasoline, so I think we are good. Or at least good enough that I accept any additional risk beyond that.
 
Not surprising at all but... your tanks and the modifications are black. Did yall have the tanks spray lined or powdercoated? Looking at the photo it does not appear at all that yall ground it down, welded the ears and then rattle canned it (that approach isnt commensurate with this level of install anyway).
ATI did all of the modifications in house. We ordered 'custom tanks' from them. But its just the standard one that they welded on angle brackets. After that as @Modman stated, they powder coated them prior to shipment. The black powder coat is a standard option they offer.
 
Here are several of my unique items. There is a pic of gauge above so I won't duplicate that one.

A bit different aesthetic on the switch. Same function, though. Momentary operation, blue ring led illuminates while the pump is running:

PXL_20240514_133941950.jpg


Here is my wiring "hub". I already had power running to the Dometic fridge using their hardwire kit. This has plenty of headroom for the Carter pump, which is relatively low draw, so I split off of it with a fused distribution block. I also mounted the relay in close proximity. There are a few areas I want to secure better but wanted to verify function, first. The Built Right panel came in handy:
PXL_20240514_134110003.jpg


The relay has two switches and a dial to adjust the time delay from 0-15min:
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Here is a view of the final install. Part of the reason I went with the Sentry CT was a long term vision of installing a tank like this. I had to be able to access the tank filler so needed something that retracted an appropriate amount. @MiTremor906 has the Revolver but that has a similar footprint when rolled up:
PXL_20240514_134137907.jpg


Note that I did have to cut my bed mat:
PXL_20231202_192245817.jpg
 
Here is the intended filler modification. ATI provides the aluminum adapter with two 3/8" welded straight hose barbs, tubing, clamps. This particular install went up thru the bed floor which we did not like:

Screenshot_20231229-114652~2.png


We did have to drill two holes for the bulkhead fittings but they are not thru the floor.

One added benefit of this tank is it can be removed fairly easily by one person. The wiring to the tank is one nut for the sender, one press on wiring clip for the ground. Remove two hose clamps and four bolts and it lifts right out. The tank is really light, being all aluminum. We had ours in and out several times doing all the package work and routing...
 
If my bed wasn't filled with the deck system, this would be an option. I am definitely think Transfer Flow as soon as I get the truck back from dealer (transmission leak).
 
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