Factory sub tank - sourcing and fitment discussion (2 Viewers)
- Thread starter grinchy
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- Thread starter
- #223
- Thread starter
- #224
Still deciding what to do with the trailer wiring
The wiring is long enough you should be able to relo it out of the way, maybe mount it pointed downward like Slee does. If you ever tow, the trailer plug needs to go into the bumper, IMO. Factory location sucks.
You considering mounting a skid plate between the frame rails to protect the tank?
- Thread starter
- #226
no. its fully above the frame rails. i am hoping to put an air tank back in the space, the sub tank is sized to go above the tire winch, so there is quite a bit of space.
however if one did want a skid, there is one available
agree that trailer wiring plug should be in bumper, but my bumper fits too tight to accommodate. i just have it zip tied up, i tow infrequently.
- Thread starter
- #228
I chose not to drop the main tank. I did this outside in my driveway and didn’t have a way to extract the main tank from under the vehicle (or lower and raise it successfully).
to remove and replace the pump assembly I cut the access hole under the middle row seat wider by 1/2” radial cuts in the sheet metal and bending it back.
To do it again I’d make more cuts - maybe 10? I used five and it was enough to easily remove pump, but getting the shape back to refit the lid wasn’t easy. More cuts less deformation easier to put back.
I thought this would be harder than it was! The hardest part was just refitting the clips to the pump hoses.
some pics of the fuel pump access attached
- Thread starter
- #229
Drove 160 miles today on Full per the gauge. 
No codes or drama so far related to the sub tank.
I did bump a power wire or signal wire on my amplifier setup somewhere and am getting a bit of intermittent ground crackle.
Sigh.
No codes or drama so far related to the sub tank.
I did bump a power wire or signal wire on my amplifier setup somewhere and am getting a bit of intermittent ground crackle.
Sigh.
- Thread starter
- #230
I joined a new forum Dual fuel sensors, one gauge - https://forum.allaboutcircuits.com/threads/dual-fuel-sensors-one-gauge.177573 and got some help on combining the fuel senders.
Success! We can put the two senders in series, and parallel with resistors to scale the readout accurarely for both tanks.
At EK1 (left side kick panel) build this simple circuit:
I don't think it matters which leg you put the sub tank sender in series on, but I chose pin 7.
The resistor values to parallel the senders with are:
A - 200 ohm - Sub tank sender
B - 850 ohm - Main tain sender
The goal is to parallel the sender potentiometers AND put the sub and main tank in series overall.
Success! We can put the two senders in series, and parallel with resistors to scale the readout accurarely for both tanks.
At EK1 (left side kick panel) build this simple circuit:
I don't think it matters which leg you put the sub tank sender in series on, but I chose pin 7.
The resistor values to parallel the senders with are:
A - 200 ohm - Sub tank sender
B - 850 ohm - Main tain sender
The goal is to parallel the sender potentiometers AND put the sub and main tank in series overall.
Reading this thread is the closest thing I've experienced to my college Sanskrit class. The details are obscure, and yet here and there I find a few words I understand, causing a semblance of meaning to emerge... before it slips away somewhere behind my knotted brow...
I am envious of your skills and accomplishment here.
I am envious of your skills and accomplishment here.
- Thread starter
- #232
Thanks for the kind words. I made it more difficult than it had to be, but sometimes that’s the way of finding the way.
By putting the two senders in series, does that mean you wire pos of sender 1 to neg of sender 2, then neg of sender 1 and pos of sender 2 would wire to 6/7 in your diagram? With no resistors added you would read the cumulative resistance of the two senders combined, so between 30-820 ohms?
It has been a while since I learned this stuff in school, I don’t remember any of the calculations. Good work!
- Thread starter
- #234
yes. The senders are inline Or ‘between‘ the two wires. So the factory sender is between wires 6 and 7. the sub tank sender is inline or between the two conductors I run up front.
ignoring the parallel resistors, we would see 30 full and 820 empty if the sub sender was added to one of the legs of the factory sender, (in series) It really doesn’t matter which leg as the potentiometer is resistance and doesn’t have a direction.
to parallel the pot, the resistors go between the conductors.
note you can make the purple highlight connections at once/same location , it will be easy to do.
I’m still waiting on the resistors, I’ll take some pics when they get in.
here’s a better drawing
edit fix a label, add second drawing
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You need to sell these as NFTs.
CharlieS
GOLD Star
I am so impressed with this whole project. Thanks for bringing us along for the ride.
Electronics scare me, so I’m not entirely sure what magic happens in this circuit. Naive question - could this be adapted to read a LRA auxiliary tank fuel level?
Electronics scare me, so I’m not entirely sure what magic happens in this circuit. Naive question - could this be adapted to read a LRA auxiliary tank fuel level?
This is wild @grinchy, the level of commitment and engineering prowess. It's a pretty intense level of integration to get the stock subtank in. Thanks for showing the way.
That charcoal canister really makes this that much harder, but again you found a way. I've been looking into various ways to maybe delete or simplify the system, but it does provide useful vapor suppression. Hope you get much enjoyment out of this mod.
I'll likely be digging in again with my LRA and charcoal canister as I'm not sure they have it configured just right. Having some problems fueling the main tank and I suspect an issue with the open vent and charcoal canister, particularly when mixed with many dusty miles off-road.
That charcoal canister really makes this that much harder, but again you found a way. I've been looking into various ways to maybe delete or simplify the system, but it does provide useful vapor suppression. Hope you get much enjoyment out of this mod.
I'll likely be digging in again with my LRA and charcoal canister as I'm not sure they have it configured just right. Having some problems fueling the main tank and I suspect an issue with the open vent and charcoal canister, particularly when mixed with many dusty miles off-road.
I had to do the math on this for it to make sense. It looks like this:
Question I have is did you verify that the senders read in a linear fashion? Meaning does (15+410)/2 = 212.5 ohm read on the gauge as half a tank?
Since you have access to the FSM you may be able to verify:
factory fuel sending unit ohm rating?
Going to switch to a fuel cell between the frame of my 2nd gen '95 4runner. Anyone happen to know offhand what the factory gauge's ohm rating is? Would like to retain my factory gauge.
forum.ih8mud.com
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The other thing to check is what 28.69 ohm would read on the gauge, since that is the lowest reading the circuit can produce that will never read completely full on the gauge since it is looking for 15 ohm.
- Thread starter
- #240
I am hoping it is at F! The stock gauge sweeps a bit to the right of F when full. 15 ohm on a 390 ohm sweep is less than 5% inaccurate when Full.
Not perfect, but not bad.
