OEM Subtank Retrofit/Install Project With Pics (2 Viewers)

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As you can see, it fits snug near the left/right chassis rails and just behind the crossmember near the springs and just in front of the rear most crossmember. It sits just above the spare tyre cross piece (removed in this picture since I have the spare on the rear).

Too cold and dark to go out and measure it on my 80, sorry :)

cheers,
george.

install2.jpg
 
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Arkansas
As you can see, it fits snug near the left/right chassis rails and just behind the crossmember near the springs and just in front of the rear most crossmember. It sits just above the spare tyre cross piece (removed in this picture since I have the spare on the rear).

Too cold and dark to go out and measure it on my 80, sorry :)

cheers,
george.

install2.jpg
Thanks! I found one in Oz. I'm trying to get approximate shipping sizes figured out.
 
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Santa Rosa, CA
Great question. Theoretically I would think that would work. Just need to be attentive to the level in main tank so you don’t over fill.
Does anyone know what signal is sent from the main tank 75% float switch?
What about using the sender from the main tank to determine the fuel level? I am wondering why they put in a separate level sensor for the sub tank system when the main tank already has a fuel level sensor in it?
 
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@OutlawMike If that type of circuit could be used to shut off a transfer pump like a Holley Blue pump you could most likely market those to members like myself who are running sub tanks without the OEM ECU and transfer pumps set up.

That is the kind of circuit I had in mind to trigger a shut off for a FP relay once the main tank reached 3/4 tank. I was going to include a OEM sub tank switch to turn the pump on.
 
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@OutlawMike If that type of circuit could be used to shut off a transfer pump like a Holley Blue pump you could most likely market those to members like myself who are running sub tanks without the OEM ECU and transfer pumps set up.

That is the kind of circuit I had in mind to trigger a shut off for a FP relay once the main tank reached 3/4 tank. I was going to include a OEM sub tank switch to turn the pump on.
I need to do some testing with the factory fuel gage and sensor to see what happens if I tap into that circuit and where it would be best to do that. I need to ensure that I do not cause errors in the main fuel gage reading when the circuit is being referenced. Once I see how that can be done, then it is a pretty simple matter of determining the resistance measurement that corresponds to a 75% full main tank and designing a simple circuit to trigger a solid state switch that would give a continuity signal output that could be used to trigger the OEM system. I do not see any reason why it could not also trigger a relay to run another type of pump. It is just a trigger signal at that point. It would be best if all of this happened in the cab somewhere, as I would not want to design something that lived under the vehicle.
 
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I think the intent, as I found out doing something slightly different, is that the full/empty sender is a float switch. The fuel level sender naturally swings up and down with movements of the fluid. The range of resistance would need to be wide enough that the pump does not get prematurely shut off during transfer because you went over a hill. The floats have less variability on the continuity switch. Once they fall, due to their buoyancy, I think it takes a bit to float them back up.

I wanted to use the factory level sender in the sub tank to drive a tricolored LED. I never could get it to work with a small voltage comparator module I got off E-bay. I'm not too good with electronics. What I ended up doing was putting a relay on the empty float switch in the sub tank so my LED light would show green if there was fuel in the tank and red if it was empty. Works pretty good, cause lets face it, you either fill the sub tank and use it, or not, you probably won't be driving around with a 1/4 tank in there. What happens though is the tank pumps down and turns the pump off, using Georges ECU, and I believe it is pretty much empty, but then the there may be enough fuel left that the light turns green again. When that happens I hit the switch again on good flat ground, and then it goes off for sure. You just have to know not to transfer fuel until the main tank is below 1/2.

What I'm getting at, is if you are looking at the resistance from the sender, this signal will be all over the place. I think to make a more concise signal, Toyota used the float switches to ensure a good solid run, or prohibition of run for the pump without the bounce of the level float.

In the 100 series, they just put a regular fuel pump in the tank and let the pumps and fuel gauge switch over from main to auxiliary. Probably simpler in the end.
 

CycloSteve

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After 11 years of use, I had to do some maintenance...The filler-diverter decided that it no longer wanted to switch over to the subtank.

So, I removed the fender liner, the linkage, and the four bolts on the innards. The pivot had some corrosion, needed TLC with an emery cloth, and some good lubrication. Cleaned everything up, and wow, it works better than 10 years ago. Two items of note; I never had the D-shaped o-ring, thus use FIPG to seal, and I have filled the little rubber boot on the pivot with grease. Hoping this will last another 11 years before needing service again.

IMG_7886.JPG
 
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LandCruiserPhil

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After 11 years of use, I had to do some maintenance...The filler-diverter decided that it no longer wanted to switch over to the subtank.

So, I removed the fender liner, the linkage, and the four bolts on the innards. The pivot had some corrosion, needed TLC with an emery cloth, and some good lubrication. Cleaned everything up, and wow, it works better than 10 years ago. Two items of note; I never had the D-shaped o-ring, thus use FPIG to seal, and I have filled the little rubber boot on the pivot with grease. Hoping this will last another 11 years before needing service again.

View attachment 2663721
Was your filler-diverter new at the time of installation?
 

CycloSteve

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Was your filler-diverter new at the time of installation?
Used and about as crusty as it looks now, and it leaked upon the first fill-up...thus my discovery that the o-ring was missing back then. Black FIPG held up fine to gasoline, and now diesel, but in retrospect I could have lubed the pivot assembly / rubber boot.

The take-away is to lube/clean if your linkage starts feeling stiff.
 

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