Simple Dual Fuel Tank Plumbing - Will this work?

[Lynn]

For years my father ran a simple dual tank setup. Two tanks, two pumps, no transfer (both tanks fed directly to the engine) with a simple toggle switch to select the pump. He only had a gauge on the factory tank, so he would run on the aux tank until it was empty, then switch over.

He got pretty deft at hitting that switch at the first cough of the engine.

 

[HenryJ]

Some links for you:
BLT Offroad Avalanche
Expeditionswest Tacoma
ThunderII - S-10 crew cab auxiliary fuel tanks

The Avalanche is my current truck. Scott Brady did the Tacoma. The S-10 was mine and inspired by Scott's install.

Notes:
1- The tee in the vent line doesn't work. It floods the evaporative emissions system. (Learned from experience.)
2- I use a momentary switch for fuel transfer. It does not take long. I add fuel around 3/4 in the main and keep it hovering between 1/2 and 7/8 most of the time. The momentary switch eliminates the possibility someone accidentally turning it on, or bumping it. This worked for both my installs and I do not see any need to change even today.


3- Gravity feed doesn't work. It will over fill the main tank and flood the evap system too. (learned from experience) An electric tank valve solves that problem as can be seen in my S-10 install.

4- The stock evaporative emissions system on my vehicles were designed to handle 100 gallons or slightly more. It can handle the added tank just fine and not over whelm the system. Mine is tied to the stock system. Keep in mind that does not mean it would pass an inspection if that is a requirement for your locale.

#Tip:#
Use hard fuel line as much as possible. If that is not an option use braided stainless fuel line. Hoses exposed underneath deteriorate at a faster rate than in the engine compartment. Spending that little extra in the install, save replacement and dangerous leaks later (learned from experience)

I have been using these systems for just over a decade now. The latest in the Avalanche is the best of everything in one. Lessons learned and improvements made.
Both fills in one location-

Dakota Digital fuel gauge reads in gallons and easy to calibrate for the fuel tank size as well as working with numerous types of sender-

Note the LED indicator and momentary switch. The LED was added later. It is a visual indicator that the relay is indeed energized. Never a problem, but comforting to me I know it is working.

Tank tucks up nice underneath leaving room to stow the bridging ladders-

This truck carries just over 49 gallons of gasoline when full. That gives me a conservative range of 750 miles. I usually fill up at between 450-500 miles.
I have found nothing I would change and it has been wonderful. Those links offer many ideas. I knew of a few more, but don't see the old links active any more. All this started a dozen years ago.

Good luck with your installs people!

 

[doug720]

Here is my dual tank system in my diesel 60 Series LandCruiser. 2 tanks that fill from the modified stock fuel inlet pipe. No gauge on the saddle tank, but my mileage is fairly consistent, so I just switch tanks at a certain mileage. If I forget, the engine may have to be hand primed, but that is rare if moving along a road. Both tanks total about 43 gallons and is good for over 800 miles.

Doug

 

[1stDeuce]

HenryJ's setup is pretty much awesome! I am hoping to do the same thing with the rear tank from an '80-96 F150, which was 18 or 19 gallons, and only about 8" tall. I run the bed tank of my diesel as a gravity feed, but I wouldn't do it with gas, as there is occasionally some leakage, not to mention the liklihood of wrecking or flooding/leaking from the evap system. (No evap on a diesel.)

Ideally, I want a dual tank system with a switch. I did this on my last truck. The switch solenoid switched not only the supply and return, but also the signal from the fuel level sensor, so my gauge showed the level in whichever tank I was using. Of course, this means you have to have a gauge in the aux thank that reads the same resistance or voltage as your factory gauge, but that's not too hard to come by usually.

If you do end up running a transfer pump, you could always use a timed switch, like the one for a rear window defrost. That way you run the main down to 1/2 tank and bump the timed switch. The pump will run for 10 minutes or so, and then shut off automatically. Win!!

Chris

 

[HenryJ]

HenryJ's setup is pretty much awesome! I am hoping to do the same thing with the rear tank from an '80-96 F150, which was 18 or 19 gallons, and only about 8" tall....

Thanks! Good choice on the fuel tank -

That is exactly the tank that I used 17.8 gallons.