adding reserve fuel tank to ‘98 k2500

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98chevy2500SS

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I think quite a few Squarebodies had dual tanks.... Fords of the same era did too, I think.
You are correct, I think it is was mostly the 3/4 ton and one tons that got the dual tanks, or at least that I have seen.
 

deadbeat

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I used to hunt with a guy with a 2001 2500 4x4 diesel. He put a tank under his toolbox, and when his tank got to 1/8 a tank, he would pull over and open the petcock on the under tool box tank, it would slowly fill his tank back to full. I drove it from Mt. Sterling KY to Crandon Wisconsin before I had to stop for diesel on a grouse hunting trip, ~ 800 miles. The petcock hooked to a line in the filler neck.
 

JayMB

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Some guys mount tahoe/suburban tanks under the bed where the spare tire normally goes. There are a few writeups on the internet about that.

It's worth remembering that gas powered GMT400's have expensive in-tank electric fuel pumps, while most squarebodys had suction fuel pumps mounted on the engine (mine does, don't know about EFI ones). This meant that they could get by with a simple valve to change between tanks. You'd need two fuel senders and some sort of valve setup (and electrical setup) to swap between them. Unless you had some small low pressure pump or gravity system to fill one tank off the other (like deadbeat's hunting buddy).

I have seen in the 0411 PCM that a lot of guys run here that there are settings for having two fuel tanks. Maybe that was a commercial truck option? (C6500 with 8.1L?) L31MaxExpress probably would know more about that.
 

Erik the Awful

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If you're junkyard scrounging, '70s and '80s Jaguar XJ6s have complicated dual 11 gallon tank setups with the appropriate switchgear. They have a set of solenoided Ys that switch flow if you apply power.

If you run an external pump, you have to switch both the feed and return lines. If you run internal pumps, you could simply use a relay to switch which pump gets power and also apply power to a single solenoid on the return line.

Alternatively, you can run big equalization tubes between the tops and bottoms of your tanks so they never overfill and simply overflow into the other tank.
 

skylark

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The hd uses a straight frame from the cab back that is 34 inches wide. A lot of people call them a ladder frame because they are straight and long. I'm 99% certain that the HD tank wouldn't work in a standard 400.
 

HotWheelsBurban

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The first generation Chrysler Pacifica (2004-2008 station wagon looking one) has a similar setup to the Jaguar. That's why Mom's got parked, those pumps are pretty expensive. The square body trucks we had for the parts store were both half ton and had the dual saddle tanks. 20 gallon on the 78, 16 gallon on the 81. It had a 2bbl 305 so it got decent mileage for a pickup. IIRC there was a big switch in the cab under the edge of the seat to change over. But this was back in the simple (carbureted) days. EFI changes everything! Good idea though, to improve range, just going to be a bit more work. Good luck and let us know how it works out
 
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