corax
Explorer
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)
*note* if you're installing the same type of tank I used, the capped off Evap Vapor Vent line at the 5 o'clock position can be used instead of drilling a new fitting into the plate
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
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)
*note* if you're installing the same type of tank I used, the capped off Evap Vapor Vent line at the 5 o'clock position can be used instead of drilling a new fitting into the plate
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
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