All my Dual/Aux Gas Tank-ers I need some wiring understanding (1 Viewer)

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My PO installed Aux gas tank and I’m curious about a couple things...

do you usually also install 2 gas gauges, or (as I think my PO might have tried) - to have have the gas tank switch and then just have one gauge that flips when switch is flipped? (Maybe that’s cockamimi) but he only had one gauge and wired both in I believe.

In regards to my wiring I’m curious how this looks ... I took some pics - I can add some context in a moment but that’s pics of underneath where the wires go to soleniod then to 2 different tanks..I’m not even sure the switch works I need to test somehow

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V8FJ4078

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You should hear a click if that solenoid is working. I had one like that in mine and you could always hear it click. I never inserted a gauge in the rear tank, but I did see a schematic here on mud before for how to do that. I always ran the rear tank til it was empty then ran off the front tank until filling up. When it sputtered, I flipped the switch and kept going on the stock tank!
 
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I have 1978 with a tank under each seat, (stock tank and a 40 litre secondary) installed 40 years ago. A small switch on the dash to switch between tanks. The valve is visible below where the drivers and bench seat meet. There is a very faint click when using the switch. I still run the mechanical fuel pump which simplifies things. The fuel gauge only reads from the stock tank so I empty the secondary first and switch when it splutters. The biggest issue is with fuel fillers on both sides, modern pump hoses aren't long enough to reach both sides for the same fill.

Newer 70 series now have 2 fuel gauges but didn't always.
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Tim
 
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Jan 6, 2003
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I have mine hooked up with a Pollak 6 port valve which is mounted under the battery tray right before the fuel pump. Each tank has a sender which automatically switches to the correct unit when you swap fuel tanks so the oem fuel gauge is reading whatever tank you're drawing from. The nice thing about the Pollak is it's only powered when it's switching, so it's not drawing any current during normal operation. Whatever valve you use be sure to put a fuel filter before it so crap from the gas tanks won't contaminate it.

Pollak Valve
 
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The 6 port Pollak valve pictured earlier is no longer sold. You can only get 6 port Ford or Chevy dual tank valves and then modify them to get them to work. I emailed the maker of the Pollak valve and they told me this.

You can use two 3-port valves, and I tried that, and one of them leaked, and I was so irritated that I ripped it all out and just run a single gas tank.
 
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The wiring the same on these? Because I’m replacing my valve and want to plug and play for most part... cheaper one looks the same as what PO had but I would go with the pollock if you tell me wiring in would be easy

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So what am I missing / Amazon sells it but the company no longer makes it? lol lock pictured previously

Also will those two pictured hook up the same? I see one red wire in one and then whatever that thing is with all the wires for the pollock
 
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The 6 port Pollak generic one (that looks like the metal 3-port one above) is no longer made - the 3 port is. The 'extra wires' are for OEM systems, rather than a home-brew setup. I'm calling the top one a 'Pollak' valve, but they are all made by the Pollak company.

What I dislike about the 6 port 'Ford/Chevy' valve is that the vent line fittings are different size and don't fit the 3/8" line on a Toyota. Amazon product
 
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The generic 3 port switching valve looks like a solenoid valve and only require 1 wire for power. It's most likely grounded through the frame. So you apply power, valve switches to 2nd tank and will stay there as long as power is applied. Turn off power and it reverts back to the main tank (or vice versa).

The 5 wires on the Pollak are for the fuel gauge and sending units and optional pump.

1 Wire to fuel gauge
1 Wire to main tank sending unit
1 wire to aux tank sending unit
1 wire to power
1 wire to ground

Only the power and ground wire is required to make the pollak valve work, but they have to be wired through the provided switch so it can reverse polarity. The pollak is a motorized switching valve, so when you apply power it turns a motor and some gears to switch. When you flip the switch, it reverses the polarity and direction of motor to switch back. It only draws power during the switching operation, all other times it just sits there dormant.

The other gauge and sending wires are optional, you just won't know what the fuel level is in the aux tank.
 
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