Triple fuel tank on a 1980 C30 dually

[Dillon Rock]

Okay, been kicking the thought around on how to go about setting up a triple tank setup. My dually has 2 20 gallon tanks and I've wondered if anyone has had or committed to making a three tank setup i.e. a suburban or blazer tank behind the axle? If so, I would like to know details and how to go about wiring in the switch and routing to gauge plus how you set up the fuel tank plumbing. I have to replace my passenger tank due to a rust hole so both will get swapped (joys of owning/working on/driving 45 year old equipment or better). Mainly the thought is for long haul (454 gets 8mpg or so with the manual) and just long distance in general.

[SCOTI]

Trying to set up 3-supply sources to one switching/routing valve seems like it would be quite the challenge.

To yield a similar result w/less switching/wiring failure points, what about 1 main/supply tank & two supplemental tanks? The two supplemental tanks could utilize simple electric fuel pumps to move/transfer the fuel to the main/supply tank.

The gas gauge & engine feed would only be tied to the main tank.

[Getter-Done]

My Daddy had a setup on his truck with a 3rd tank.

He was a Mechanic for an Excavating Company.
He put a Million miles on that truck.

He would fill the 3rd tank up and run the truck on the 3rd tank without a gauge.
He would run on it till it run out.
Then he would swap down till he was using the one with a gauge.

You could add a separate gauge for the 3rd tank if you choose too.
If that tank has a sending unit.

Best I remember He used a 3-way Boat valve.

Maybe like this :
Link: https://www.amazon.com/Moeller-Fuel-...ng_fplfs&psc=1

[D.B]

Yes, a 3-way manual fuel valve will work to control the fuel. And if all three tanks have a sending unit you can get a 3-position rotary switch to control the fuel gauge.

[Dead Parrot]

Don't know if it is still made but JC Whitney used to sell a 30 gallon side saddle tank that fit where the 20 gallon does. IIRC, you had to rework the fill spot. But it would let you have 50 gallons without rework of your valve plumbing and gauge wiring.

A long ago co-worker had one on his 75 w/454 manual trans. His got 6 mpg. Used it to tow a 5th wheel travel trailer.

[Dillon Rock]

Originally Posted by D.B

Yes, a 3-way manual fuel valve will work to control the fuel. And if all three tanks have a sending unit you can get a 3-position rotary switch to control the fuel gauge.

So kind of like how the 73-75 trucks were with the manual selector valve on the left side of the seat? Also, for a 3 position rotary switch, if memory serves me right, that's a 6 pin connector vice 5 pin like the selector switch for the 6 port style from 77-80?

[Dillon Rock]

Originally Posted by SCOTI

Trying to set up 3-supply sources to one switching/routing valve seems like it would be quite the challenge.

To yield a similar result w/less switching/wiring failure points, what about 1 main/supply tank & two supplemental tanks? The two supplemental tanks could utilize simple electric fuel pumps to move/transfer the fuel to the main/supply tank.

The gas gauge & engine feed would only be tied to the main tank.

I was actually thinking about this earlier today with the two 20 gallon saddles being main supply and the 40 gallon behind the axle being the supplementary tank to fill them. Trick would be setting a cut in/cut out method for filling.

[Dead Parrot]

Originally Posted by Dillon Rock

I was actually thinking about this earlier today with the two 20 gallon saddles being main supply and the 40 gallon behind the axle being the supplementary tank to fill them. Trick would be setting a cut in/cut out method for filling.

Reverse it. Make the rear 40 gallon the main tank and the two side tanks supplemental. When the main tank is below 1/2, refill by emptying one of the side tanks. Avoids the issue of accidental overfilling.

[D.B]

Originally Posted by Dillon Rock

So kind of like how the 73-75 trucks were with the manual selector valve on the left side of the seat? Also, for a 3 position rotary switch, if memory serves me right, that's a 6 pin connector vice 5 pin like the selector switch for the 6 port style from 77-80?

I think you are on to something.
I had a 69 GMC with three tanks. One behind the seat and two saddle tanks. I hated the manual valve and not knowing how much fuel I had once I switched off the main tank. So, I contacted a company that made rotary switches and explained to them what I wanted. They gave me a part number for a switch that worked. It was a dual-purpose rotary switch used to control the electric fuel pumps I put in the tanks. I also installed one-way check valves to keep fuel from being routed into the unused tanks.