Auxiliary 17 gallon fuel tank 'idea'

We had a Downey Toyota auxiliary tank under the bed where the spare would normally go on our 1988 Toyota 4x4. Held an extra 15 US gallons iirc, no pump (just gravity)- as it had a hose that connected to the bottom of the original fuel tanks drain plug and as the main fuel tank emptied it was replenished by the auxiliary tank. So the fuel gauge was something to get used to- would stay full for the first 2/3rds and then would go the same as before the auxiliary tank was added. I started to search for one for our 2nd gen- but to no avail...

First idea was to put a kit together and sell them- but since I am still recovering from nerve surgery on my neck and fore arm it is unlikely that I will get to it any time soon. So I thought I would put the info I found out there for anyone that wants to try it (or if a vendor wants to pick it up and run with it).

*First off for those afraid of cutting & welding on their truck turn back now...


-my idea requires the rear 'X' member/ spare tire carrier to be cut out of the truck.

-Then plate the rear frame; Here is a 2nd gen rear frame plate kit that requires you to cut out/ remove the 'X' member.
Made by TW member- jeffzOrz ($120 shipped!)
https://www.tacomaworld.com/threads/2nd-gen-frame-box-plate-kit.405001/

-Make up a couple cross members to go in front of and behind the auxiliary tank- add mounting brackets to the cross members for the Auxiliary tank and maybe even a skid plate.

-Found a 1941-54 Buick steel tank that I think will work well (it's steel, so its easier to cut and weld if needed).
17 gallons
Length (in):31.500 in.
Width (in):27.500 in.
Height (in):7.500 in.
($250);
https://www.summitracing.com/int/parts/tnk-b1-b/overview/

-Weld a AN bung or barber fitting to a low point to drain the fuel into the oem tank. (~$8)

-Gravity would be used to transfer the fuel (no pump), run an AN bulkhead fitting through the OEM tanks fuel sender lid;

http://www.davidebsmith.org/cycle/fuelcell/FuelPumpPlate.jpg

and attach a tube that extends almost to the bottom of the tank. Should work the same as drilling a hole in the bottom without the draw backs. Something like this. ($50);
https://www.strictlydiesel.com/p-2678-driven-diesel-58-fuel-tank-pickup.aspx

-A fuel shut off might be nice to have on the auxiliary tanks transfer drain so that you could isolate the tank if needed.

-A filter between the auxiliary tank and the OEM tank.

-The auxiliary tanks venting would be tied into the OEM tanks venting to maintain a closed system. (that is how it was done on our Downey Toyota set up).

-Cut/weld/paint a second fuel door between the rear wheel and the tail light. Could paint a strip or use vinyl to cover body worked area to avoid paint work. ($115);
http://www.speedwaymotors.com/Hagan...gn=CSEGOOGLE&gclid=CL-Hg5bpvdICFRq1wAodn7oLdw

-Was also thinking that with the tank only being 7.5", there may still be enough room to carry the spare under the tank. Would have to make a swing down cradle- but the new crossmember will give something to mount it to. Would be nice to retain the spare tire under the truck- even if it hangs somewhat lower.

-Also figure I need to get better rear springs, Timbrens or airbags for the rear to deal with the extra weight as well as for towing- so I won't attempt the auxiliary tank for a while.

~ $600 worth of parts once you get the fuel hose, clamps, nuts & bolts, AN fittings, etc. Then the labour to plate the frame and weld in custom cross members (maybe $50 for a couple 2x3 stock?).

***EDIT***
Starting to wonder if there is enough height difference between the two tanks to make the transfer work effectively.

-I think it would be faster and easier to go the same route as HolyHandGranade with a pump and spliced into the filler tube;

Really liking the fuel gauge for the auxiliary tank as well. With the check valve in the pump it you will be able to isolate the tank if needed.***

 

For that kind of money and that you want to still carry spare underneath I would just get three five gallon cans. You would not have the convenience of it functioning as one tank. I normally would take a break from driving before going thru a whole tank. While taking a break just throw another five gallons in.

 

Yeah, it is more for people that want an extended range without giving up any cargo space, keeping the centre of gravity lower than storing fuel in the bed or on a rack/ roof and I for one would not want to deal with the smell & mess of pouring fuel from a jerry can into the truck- then having to store the usually wet and smelly jerry can in the box of the truck where it can get on other stuff and that is not even taking into consideration the environmental impact I would have trying to pour 15 gallons into my truck- with the amount of fuel I spill just filling the lawn mower...

The same as guys that go to the trouble and expense to add on board air- I mean they could just use a compressor at home or go to a gas station...

For me it is more about my truck fitting my needs/ wants. I don't want to deal with jerry cans (or fuel in general) so spending the money to add an auxiliary tank makes more sense for me- besides I really liked the one we had in our last Toyota.

 

I like this idea.

Curious though, would the aux tank need to be vented to the atmosphere, so the gravity feed doesn't create vacuum on the second tank? Or maybe run a vent line from the top of one tank to the other so its still a closed system?

Also, the tube that extends to the bottom of the 1st tank, would that need to be as the same level as the drain of the 2nd tank, or would it need to be lower?

 

you would, if its properly setup as a gravity feed, it would just act as one huge tank. however, you would need to get the gravity part correct, and not sure how possible that would be.

 

Thanks, forgot to add that part, the auxiliary tank we had from Downey Toyota tied into the OEM tanks venting so it was still a closed system (ran a 22RE and then a 5.0L V8 with full EFI). It was connected to the OEM tank with a brass 90* fitting that replaced the drain plug on the bottom of the tank. Couldn't have been more than 1/2" high inside the tank- so I figure having the fuel sender transfer tube stop a 1/2" (or more) before the bottom of the tank- would be happy to hear others input on the ideal height? I am sure there is some engineering formula out there that would tell how far from the bottom to place the tube based on fuel weigh, etc. As long as the bottom of the tube is lower than the transfer drain on the auxiliary tank it will drain into the OEM tank as room is available- as paranoid56 said- it would act as one large tank- just have to get the tube height right. I think that needs to be right to prevent pushing fuel into the charcoal canister as another member pointed out to me;

On our old Toyota the height difference between the Downey auxiliary tank and the OEM tank was less than 12" and used a 3/8' rubber fuel line to transfer the fuel. I think the Downey auxiliary tank was 15 gallons.

Just found this guys auxiliary tank set up on his motorcycle;
http://www.davidebsmith.org/cycle/fuelcell/fuelcell.html

 

Here is another option for a 2nd gen aux tank;

https://www.tacomaworld.com/threads/piecing-together-an-aux-fuel-tank-setup.475581/

 

I am over jerry cans! How many times does one have to fill their truck this way before they lose their freakin mind! It always happens right at sunset, after a long day, your tired as shit and you need to catch up on your track lines to make camp. After a week on the trail, you start to think about the small things that could make life easier.

 

I'm super into this idea as well. It's beyond my engineering capability to devise such a system myself, but this is something I'd support any way I could and get behind installing myself.

 

Can't seem to get the pic to show up, so here is the link;

https://s-media-cache-ak0.pinimg.com/originals/b5/cb/8b/b5cb8be7f62dda897341924bd5d2957e.jpg

 

Are those rotopax fuel containers? How are they hooking up the hose and pump to them?

 

Doubt they are hooked up- it's just where they are stored I believe.

 

I was just thinking of doing this same thing with rotopax in the spare tire well, too. Simpler and way faster to pull off than a whole new tank system; far less tech knowledge needed.

Where'd that pic come from?

 

also found over on t4r; mounted a rotopax 4 gallon in his spare tire well.

 

Besides an extra area to store your rotopax at, I could not see myself doing it this way. There are more convenient locations to hold the rotopax then under the truck. Even if these where plumbed in some how, I think the minimal amount of fuel capacity that you gain while using that space is counterproductive. If the spare tire area is to be used for additional fuel, I think a custom tank would be much more efficient as to provide a larger capacity. This is just my opinion.

 

Pinterest.

I will be doing a tank not the root packs- just thought it was an alternative to carry extra fuel without losing bed space or raising the centre of gravity. I want to deal with fuel as little as possible- so a full custom set up will be plumbed in.

 

I agree, having that under like that is just weird. to much of a pita to get to. I am also thinking about the ford style tank, plumb it into the filler of the old one and use a pump or solenoid (depending on height) would also be nice to be able to have both fillers in the same opening.

 

I was originally thinking of putting them both behind the fuel door- but after having a good long look at it- I don't think there is enough room and the routing looks problematic, so I removed it from the original post. I am thinking I will be going this route;

-Cut/weld/paint (or put a decal or vinyl to cover the body work and avoid painting) a second fuel door between the rear wheel and the tail light. ($115);
http://www.speedwaymotors.com/Hagan...gn=CSEGOOGLE&gclid=CL-Hg5bpvdICFRq1wAodn7oLdw

Hmm... Not sure if there is room or if this will work- just thought of welding the filler necks together right before the cap- then you would have one gas cap- but when you remove the cap there would be the fill hole for the oem filler neck and then a fill hole for the auxiliary tanks fill neck. Both sealed under one gas cap.

Going to see if I can find a pic of what I mean- will add it if I do.

***EDIT***
Found some pics and I am once again leaning towards two filler necks behind the stock fuel door;

Dual Filler Neck
filler-jpg.128609

OEM Toyota dual filler neck
filler2.jpg

Pre '95 Dual 80 series filler neck(s).
https://forum.ih8mud.com/threads/brand-new-dual-filler-necks-for-80-series.582889/

A good write up on installing/ plumbing an auxiliary tank;
https://forum.ih8mud.com/threads/factory-auxiliary-sub-tank-install.818551/

 

After searching, reading and looking through countless pics- I think the best/ cheapest way is to modify an oem filler neck so that the auxiliary tanks filler neck is welded into the oem filler neck- just after the fuel cap- so that when you open the fuel cap there is the option of inserting the fuel pump nozzle into the front oem tank filler hole or insert the fuel pump nozzle into the rear auxiliary tank filler hole (difficult to say without sounding dirty!). Much the way this one is done;

https://forum.ih8mud.com/threads/poor-man-auxiliary-tank-installation.911718/page-2

The second part is the transfer tube- drill an elongated hole in the oem filler neck near where it attaches to the oem tank and insert a length of metal tubing that will extend how ever far you want/ need it into the tank- longer if you do a gravity transfer without a pump or just past the inlet if running a pump. Then weld the metal tubing into the filler neck leaving enough to attach the fill/ transfer hose (a flare or barb on the end the hose attaches to). Then coat it with POR fuel tank sealant or something comparable.
That way the oem fuel cap seals both tanks and there is no body work and less parts needed.

Also liked Holyhandgrenades fuel gauge set up- but I still need the 4wd switch where it is- but the other side... Drill a hole and use a little bondo to build it up, would be a good spot for the auxiliary gauge.

 

Lots of good info in this link- even though its for a FJ- the same plumbing applies.
http://www.george4wd.taskled.com/auxtank.html