Fuel transfer pump for aux tank?

[corax]

I got a NWMP aux tank for my 88 4runner a few months ago. I cleaned all the rust off and POR15'd the thing so its ready to go in except I'm not sure how I want to get the fuel into the main tank. 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. Problem with this is 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 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 I'm afraid it'll leak.

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. So I guess my question is if anyone has experience with "solid state" fuel pumps? I can't find anything saying they are safe for short periods of dry running and likewise nothing about how they work except that they do not use a diaphragm. Does anyone know anything about Solid State pumps?

[Good Times]

I don't think a solid state pump is required for this job. Any ol electric fuel pump would work with a simple switch to turn the pump on/off.

connect the outlet of the aux pump to a T fitting in the main stock filler. then connect another T fitting from the stock filler vent (this vents the gas when you fill your stock tank) to a return inlet on the aux tank.

it's basically a big loop. if you ever forget to turn the switch off it'll just overflow back into the aux tank via the filler vent. this should keep your pump from going dry :)

[corax]

That's a good idea, but the aux tank is only 14 gallons and the main tank is 16 gallons. So if I wait till the tank is low, there might not be enough to flow over back into the aux tank. I guess I could use the aux tank to top off once the gauge hits 1/4 tank and shut it off when I hit the full mark . . . but I'd still like to know if a solid state can take running dry (besides, I found several for under $20)

[corax]

I think I have it figured out. :clap: 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

http://i280.photobucket.com/albums/kk171/batardsalamano/auxtanktransfer.jpg

Red: fuel lines
Dk Blue: wiring
Parts: low pressure NOS fuel safety switch (adjustable 2-5psi), fuel pump, momentary & toggle switches, relay, slight fuel line restriction (small crimp in steel fuel line to main tank)

- the toggle switch turns on the system, but the relay won't turn on the fuel pump until there is ~3psi at the low pressure switch
- press the momentary switch to bypass the pressure switch and turn on the relay and fuel pump
- pressure builds behind the restriction and makes the pressure switch close, the momentary switch can be turned off now as the relay will stay on
- when the aux tank runs dry the pressure switch opens deactivating the relay and fuel pump

if I really want to get fancy, I was thinking I could run a wire from the + side of the fuel pump back up to the switch panel through an LED and on to ground as a fuel pump indicator light