Switchless duel tanks on M1008

I’m thinking about doing duel tanks on my M1008 but I really don’t want the switch in the dash or weak valve system that goes with it. While working on a 97 C7500 Chevy I noticed the duel tanks were controlled by a module and I would like to see if it could be used in mine. I’m going to use sending units from a 87 civilian truck and in tank pumps but the pump shouldn’t really matter in the detail of this. The question is if the sending unit will have proper resistance to make the secondary pump turn on and off properly. Any input is appreciated.

I too am planning on adding a factory auxiliary tank and like yourself I don’t want the switch. I’m also planning to install a factory 4000 RPM tach in place of the existing fuel gauge. The tach has a small fuel gauge in the bottom which I also dislike, so here’s what I am considering - I’m thinking about using 2 stand-alone aftermarket fuel gauges so each tank’s fuel level can be instantly known at all times, and mount a manual 3-way valve through the cab floor under the seat for switching. The only thing I will need to determine is how to plumb the fuel return line. May need to split that as well to prevent sucking from one side and returning fuel to the other. Or maybe that would be OK, I don’t know.

I considered duel gauges originally but with trans temp, electronic trans control, tach, boost, egt gauges, and ac my dash is getting very busy. I use this thing for camping trips at over 600 miles so knowing what’s going on is crucial but I really want to simplify the fueling processe to fill and go. If this works though it’ll give a second tank to anyone trying to keep a factory look so there could be benefits for many.

Sharecropper said:

I too am planning on adding a factory auxiliary tank and like yourself I don’t want the switch. I’m also planning to install a factory 4000 RPM tach in place of the existing fuel gauge. The tach has a small fuel gauge in the bottom which I also dislike, so here’s what I am considering - I’m thinking about using 2 stand-alone aftermarket fuel gauges so each tank’s fuel level can be instantly known at all times, and mount a manual 3-way valve through the cab floor under the seat for switching. The only thing I will need to determine is how to plumb the fuel return line. May need to split that as well to prevent sucking from one side and returning fuel to the other. Or maybe that would be OK, I don’t know.

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I did the valve through the floor by removing a factory plug. The one I used handles the return line as well. Here is a link to it: https://www.groco.net/products/valves-seacocks/fuel-valves/fv-6-port-series

Jamestown Distributors had the best price when I was buying mine...

Reminds me I need to fab up the cover for it...

The proper Tach for the C/K 10 through 30 had no fuel gauge in it.
The fuel gauge moved to the lower left corner where the clock option was.

If your Tach has a fuel gauge in it then it's from a larger C40,50,65 and up.
Tom

Who are you going to be dueling? Are you going to after hapless travelers? Or maybe reverse roles, and go after big rigs?

https://www.youtube.com/watch?v=h-6A79qTFNg

TGP (IL) said:

The proper Tach for the C/K 10 through 30 had no fuel gauge in it.
The fuel gauge moved to the lower left corner where the clock option was.

If your Tach has a fuel gauge in it then it's from a larger C40,50,65 and up.
Tom

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Yes you are correct. But the proper tach was a 5000 rpm gauge, and for a diesel with a sweet spot around 2000-2400 rpm, the needle was always in the lower end. The “big truck” tach was a 4000 rpm gauge and therefore the gauge needle is more responsive in the lower end. Those 4000 rpm tachs have the small fuel gauge in the bottom which makes it difficult to ascertain exact fuel level, especially when getting close to empty and after a couple beers after midnight. I happen to have a brand new NOS Delco 4000 rpm tach I intend to install in place of the factory large fuel gauge, but will abandon the midget fuel gauge in the 4000 in favor of a large AutoMeter fuel gauge. Two of them in fact, one for each tank. There is another thread on here a few weeks back which provides details of how to install that 4000 rpm tach in our CUCVs.

Mad Texan said:

I did the valve through the floor by removing a factory plug. The one I used handles the return line as well. Here is a link to it: https://www.groco.net/products/valves-seacocks/fuel-valves/fv-6-port-series

Jamestown Distributors had the best price when I was buying mine...

Reminds me I need to fab up the cover for it...

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Tex - I have an account with Jamestown Distributors and will order the valve tomorrow. Which valve did you buy? There are 2 listed, 1 “L” shape rotation and the other is a “T” shaped rotation.
Thanks.

Sharecropper said:

Tex - I have an account with Jamestown Distributors and will order the valve tomorrow. Which valve did you buy? There are 2 listed, 1 “L” shape rotation and the other is a “T” shaped rotation.
Thanks.

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I used the FV-65038 myself. I can switch between the two tanks and shut it off as well. Adds some more security when I start driving it more.

Confirmed that the module listed above will control two tanks and act as one. Secondary feeding primary using fuel senders to regulate the secondary pump. It also uses sending units together to control fuel gauge as in both tanks being full it shows a full tank. when secondary is empty and primary is full it shows half tank and so on.

i installed the aux tank a few years ago from my old 81 chevrolet 3/4ton as well as the wiring,switch and valve. no issues since 81 on the first truck it was in and none in the cucv since.

Your Correct.
The OEM system works very well.
Have had one valve failure on 4 K30's in 30 years
Tom

MarcusOReallyus said:

Who are you going to be dueling? Are you going to after hapless travelers? Or maybe reverse roles, and go after big rigs?

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This whole thread is a grammatical train wreck.

Mad Texan said:

I did the valve through the floor by removing a factory plug. The one I used handles the return line as well. Here is a link to it: https://www.groco.net/products/valves-seacocks/fuel-valves/fv-6-port-series

Jamestown Distributors had the best price when I was buying mine...

Reminds me I need to fab up the cover for it...

Click to expand...

I just ordered the FV-65038 valve from Jamestown Distributors. Thanks for your help.

Firejoker554 said:

Confirmed that the module listed above will control two tanks and act as one. Secondary feeding primary using fuel senders to regulate the secondary pump. It also uses sending units together to control fuel gauge as in both tanks being full it shows a full tank. when secondary is empty and primary is full it shows half tank and so on.

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After reading how this works that's an interesting alternative! Curious to see how you do it!

How much does the valve cost?

ken said:

How much does the valve cost?

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$144 + shipping. My daughter’s inheritance fund will never miss it.