OEM Subtank Retrofit/Install Project With Pics (1 Viewer)

Tedward

95 LC
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Feb 2, 2015
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Cleveland OH
Thanks to elmariachi, Romer , pkelly72 , george_tlc and others for the information I used to install a sub tank.
Used @george_tlc printed circuit board. Thanks for making these and your website!
I can try to assist/answer questions for folks in the future.
 
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Apr 11, 2019
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NJ
Since 99% of the wiring is already in a US-spec truck, how does the dash switch get connected? Is there already a hidden connector like the center diff lock behind the dash? Or do you need to make your own harness to bring down to the kick panel?
 
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Mar 31, 2012
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Gotha, Florida (near the dog)
Since 99% of the wiring is already in a US-spec truck, how does the dash switch get connected? Is there already a hidden connector like the center diff lock behind the dash? Or do you need to make your own harness to bring down to the kick panel?


You have to make your own (switch, pig tail behind the switch) then tap into some other wires for the backlighting (rheostat) and then route the others to the ecu (and overhead console I believe)
 
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Does anyone happen to have the weld-in ring stencil for the main tank level sensor? I will be welding in a bung into my US - Spec tank. Thank you very much in advance!
 
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Erie, Colorado
From what I can tell, the fuel level switch is no longer available. If no one has the template and the switch is NLA, could you theoretically just tie the wires together to fool the ECU into thinking the main tank is low and permitting the transfer?
 
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From what I can tell, the fuel level switch is no longer available. If no one has the template and the switch is NLA, could you theoretically just tie the wires together to fool the ECU into thinking the main tank is low and permitting the transfer?

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?
 
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I’m in the process of installing the sub tank. Is the US spec body not have all the mounting points for the transfer pump and heat shield? I found 2 existing nutserts for the pump assembly and 1 for the heat shield. Looks like others in the past just drilled into the cab. Also, 2 of the feet on the transfer pump are a tad short to make contact with body. Am I missing something or do US trucks not have all the mounting points?
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US trucks don’t have all the mounting points. Mine was secure enough with just 2 bolts and loctite. Others have drilled the floor. I recently got back from a trip where 500 miles were off road and it didn’t budge.
 
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Dec 29, 2005
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I made a bracket of sorts with two bolts welded to a thin strap of metal. Drilled holes through the floor in the valley of the needed floor rib and dropped the bolts through the holes letting the strap lay in the valley. Then I sucked it down with a nut as I recall. Made studs basically on the underside that I used to hold a heatshield I made up by the exhaust pipe and to hold the right side of the pump bracketry. I used the existing holes on the left end. I did not have any of the original heat shield pieces, just the pump and solenoid brackets. The strap welded to the bolts makes it so they won't turn on you later, and you don't need an assistant to hold wrenches in the cab.
 
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I’m in the firmament process right now. Making measurements to drill the holes.
do your pump assemblies also have the space between body and two of the mounting feet?
Any photos of what an oem setup looks like bolted up?
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I did the install this spring, and I honestly can't remember if there was that gap. Don't know when I will have a chance to look, winter has started here, things are muddy and cold at the moment.
 
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I took a look at this every-way possible and the only way to secure is by drilling. That is what I did. I drilled two holes that secured the pump assembly and heat shield in place. This of course is in addition to the 3 factory mounting points with nutserts.
I also ran the wiring harness from the overhead console. Time for the harness modification and then putting back together.
Put a fresh coat or POR15 behind the tank to not visit this area for years.
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To answer my own post (#352), the green circled mounting points are for a short piece of hard tubing that connect the solenoid valve and sub tank suction. I found it in my pile of parts.

As of today I have completed:
- mounted the pump assembly after coating it with POR15
- Made the wiring harness for the overhead console (sub-tank level and altimeter). snaked it through to the kickpanel
- Made a mounting ring for the main tank 75% level sensor. I will attach the STL file I made later on.
- Sent the main tank to get the ring welded.
- Installed the sub-tank rivnuts. Not a bad process. Below are some photos of my "tool" setup. Worked without a snag. Used a Dremel to open up the existing hole to fit the rivnuts. Purchased rivnuts from McMaster (part # 95105A199, Zinc-Plated Steel Heavy-Duty Rivet Nut, Open End, M10x1.50 Interior Thread, .7-3.8mm Material).

Still to do:
- Modify wiring harness
- Install transfer ECU
- Install dual filler neck
- Install filler pipe and association hoses.
- Install main tank wiring harness
- Install dash switch
- Test system.

Picture 1: The overhead console wiring run. Wires still attached to fish tape.

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Picture 2: I drilled out the nut then slipped it over the bolt followed by washer and rivnut. Insert into hole and tighten down the bolt.
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Picture 3: Rivnuts above frame installed.
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Picture 4: One of 2 penetrations inside the cab to mount transfer pump underneath.
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Picture 5: Steel ring for main tank 75% level sensor.
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