corax

I finally had time to finish the aux tank transfer pump wiring. It's supposed to be a gravity feed system with a hose running into a fitting where the main tank drain plug is on the bottom. The problem with this is that I don't like the idea of having something hang even lower off the main tank, especially a brass fitting that could drain all my fuel if it gets hit hard enough.

So I thought of putting a shut valve on it (elec or manual) and have the aux tank drain into the filler neck vent tube for the main tank, but the filler neck is too high and I don't want to put a hole lower than that in the side of the main tank because it'll probably leak eventually.

My final option is an electric fuel pump, but fuel pumps can get damaged when they run dry from heat build up and I would have no way of knowing when to shut off the extra pump. I can't find anything saying they are safe for short periods of dry running.

This is what I came up with, though it may be a bit over engineered it should save the pump from running dry, and if the rest of the system wiring fails a jumper wire across the load side of the relay will still turn on the fuel pump.



Red: fuel lines
Dk Blue: wiring
Parts: .25gpm flow switch found on Ebay for $4, fuel pump, momentary & toggle switches, relay

- the toggle switch turns on the system, but the relay won't turn on the fuel pump until there is flow
- press the momentary switch to bypass the flow switch and turn on the relay and fuel pump
- fuel starts to transfer and closes the flow switch, the momentary switch can be let go now as the relay will stay on
- when the aux tank runs dry the flow switch opens deactivating the relay and fuel pump

I also ran a wire from the fuel pump V+ side of the relay to the switch panel through an LED and on to ground as a "fuel pump on" indicator light

Installing the tank is easy, so I'll leave out the bits about drilling holes and bolting it up. It's the details that'll make it trouble free in the long run . . . like an exhaust heat shield so the gas doesn't get too hot (excessive vapor/boiling)


view from the wheel well


transfer pump (universal, for a carb'd car) - I used 1/4" riv-nuts to attach it to the frame rail (there is an inline filter on it now)


a bit of protection to keep the hoses from chaffing against the frame rail, it also keeps them tied together nicely so they don't move around much


here's the flow switch I used (if says "water" but I looked it up and the material that the internal parts are made of shouldn't be affected by fuel)



a few months ago I had to repair the main tank fuel pump bracket because the metal line on the outside finally rusted through, while I was at it I added an extra line to dump the fuel from the aux tank into the main tank (9 o'clock), I had actually extended that fitting down to the bottom of the tank in the hopes that it would work like a siphon once fuel starts flowing (in case the pump fails/doesn't work out I could still use the aux tank w/ pump removed)


I tossed my spare tire back under there and noticed that the tank didn't affect my departure angle at all (+ I can easily fit a 33" spare now), though if I drop off an obstacle the spare will definately take the hit. If I know I'm hitting any rough trails I'll just take the spare off and toss it in the back. I am planning on making some kind of spare carrier for the rear bumper - I always liked the idea of being able to carry 2 spare tires for longer trips.

rear view


Switches installed - turn the toggle on, press the momentary switch till there's enough liquid to trigger the flow switch, let go of the momentary and the pump runs till the toggle is switched off or the pressure in the line drops (aux tank empty) - the blue LED is wired to the transfer pump V+ wire so it is on any time the pump is running (click pic for video)


With the extra fuel on board I should be able to get a range just shy of 600 miles normal driving
(17 gal factory tank + 14 gal aux tank) x 19mpg = 589 miles

myyota

I like the set up, were did you get the tank from ?. I came across an article a while back were they used a gas tank from a chevy blazer and mounted it in place of the spare tire on a 84-88 4Runner. I was thinking of doing this sometime in the future my self.

corax

Thanks, the tank is from Northwest Metal Products -> http://www.nwmp.com/
I got it used, but it's in good shape for being 19 years old (IIRC, the date stamp on it is 1991)

4Crawler

iTrader: (3)

I've been running a NWMP tank for about 12 years now. Mine was the old gravity feed setup but in the process of converting to a pump transfer setup.

awsumfn

I installed a 23 gallon fuel tank from a early Bronco in the same location. You can see pictures at my post "23 Gallon Fuel Tank" @ https://www.yotatech.com/forums/f123...nstall-215473/ . I also made a new spare tire carrier show in a post @ https://www.yotatech.com/forums/f88/...arrier-216366/

corax

I fixed the fuel pump plate before I installed the NWMP tank or I probably would have used the capped off evap vent at the 5 0'clock position . . . just something to keep in mind (top of tank fitting is already there for you)

wyoming9

iTrader: (1)

Good job!!!!

now you can come a few miles west.

I bet you could do another one a whole lot quicker.

I still need to look at this unique vehicle in person

corax

Maybe at the Rausch Creek Fall Crawl (if there is one this year). In a few months I'll be a couple thousand miles west again

Albin

Might have been mine. NOS Blazer diesel tank from Coleman's Surplus (no longer offered last time I looked), McMaster 3/8" ball valve, Fram in-line filter then to the NW Metal Products gravity feed fitting for the bottom of my OEM '85 4runner tank.

+45 gallons of fuel when out exploring desert ghost town, secret air force bases and hot springs.

PM me with an e-mail address if you want pics, can't post'em here for some reason.

Thanks

Al

91diesel

reviving an old thread.
Corax, I'm doing an aux tank install and was interested in copying your pump wiring idea (I'm using a jeep grand cherokee tank and pump). My question involves where you got that flow switch from. I've seen one on amazon for $180!! (goes against my cheapness) Is there a cheaper way? or did you just luck out and someone had this laying around and didn't know how much they were? If this is the price, I think I may just try using some NOX pressure switches with a reducer to actually make pressure to activate them.

corax

I just ebay'd "flow sensor" and picked one based on the material it was made of (resistant to fuel) and the the actual flow rating (so the pump can trip the switch). There seem to be a bunch of magnetic reed switch ones made of steel that might work (almost all say they're for water), but I'm not sure about the longevity of a magnetic reed switch operating a relay.

If you ebay GEMS flow sensor, there are a couple for less than $30 . . . just read the description (or check the part number at the manufacturer site) and look up the materials used to make sure they're fuel resistant.

A pressure switch would also work if you can find one that triggers at a low enough psi - like you said, just have a slight restriction after the switch (main tank side) so it can build pressure. I was also thinking of using an older motorcycle oil pressure switch - my '79 Suzuki used a low pressure system, so the switch was actually a flow switch not a pressure switch (just have to machine/build/fab a housing for the switch).

91diesel

Thanks. Just got my bed back on and put the 1st 6gal in it. was wiring up my pump switch/relay and fuel gauge and kept blowing fuses. Couldn't figure out what I was doing wrong until I finally just started checking every component and the new switch I got was shorting out. Hours wasted! I'm taking a trip and will just have to remember about the fuel pump for now. When I get back I'll look on ebay (I've avoided it for a long time now.....)
Thanks again and I'll post my write up with pics when I get back.

corax

No prob. If you could, just post a link to your write-up in this thread so people can follow the links and see how else it can be done. Good luck and keep it rubber side down

corax

Someone had a question about this setup and I figured I'd copy/paste it here in case anyone else had the same question.
BTW, 6 years later and it still works perfect
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Thanks!
OK, not sure about the one you got, but the one I got has the wire diagram on it


On mine, the ground side from the relay coil went to the black wire on the flow sensor. The Orange wire went to the toggle switch, the toggle switch gives it a ground. The Black and orange wires are N.O. (normally open) but close once the sensor sees fuel flow. With those contacts closed, the toggle switch (as long as it's switched to ON) is then giving the relay a ground which gives power to the pump. When flow stops, the contact open which turns off the relay and the fuel pump (so it doesn't run dry and go bad).