Auxiliary Fuel Tank

[torinoracer29]

I scored this pretty cool 60 gal diesel tank off a military 6X6 truck and I would like to install it in the bed for long trips but I have few questions. It has 3/8" fuel supply fitting a 5/16" vent fitting and a single pole sending unit.I would like to tap the fuel lines and use manual switch over valves but I am unsure of the venting and proper routing to insure correct operation, what valves to use and a good place to get the parts. Will it mess with the electric switching valve tapping into the fuel lines for the auxiliary tank. Any ideas or help would be greatly appreciated.

 

[franklin2]

The aux units you buy in the store run the output of the aux tank to the filler neck of your original tank. So you use it for filling the tank like you would at the filling station.

Do some searching though, I think they had it designed so it would not overfill the regular tank.

 

[MIDNIGHT RIDER]

I scored this pretty cool 60 gal diesel tank off a military 6X6 truck and I would like to install it in the bed for long trips but I have few questions. It has 3/8" fuel supply fitting a 5/16" vent fitting and a single pole sending unit.I would like to tap the fuel lines and use manual switch over valves but I am unsure of the venting and proper routing to insure correct operation, what valves to use and a good place to get the parts. Will it mess with the electric switching valve tapping into the fuel lines for the auxiliary tank. Any ideas or help would be greatly appreciated.

The electric valve will soon fail anyway; so, now would be a good time to get TWO WeatherHead brand FOUR-WAY manual valves, one for DRAW and one for RETURN.

I doubt that 5/16 fitting you mentioned is a vent; more likely it is for a return-line.

Without actually having the tank to look at, it is hard to say for certain; but, any vent should be at least 1/2".

No special plumbing is required for a vent, so long as it's top end is located such that water is unlikely to enter the tank.

Not totally necessary, but I do TEE all three of my tank vent hoses together into one main open-ended vent located high and dry.

Should I forget to switch the RETURN valve to the proper tank and thus over-fill a tank, the excess will go into the vent lines and gravity feed into whatever tank has room for it, preventing the fuel getting pumped out on the ground.


I located my manual valves alongside the outside of the frame-rail, with the operating stems protuding through holes drilled through the floor.

The stems/handles are on the side of the "seat hump" on the driver-side, between the seat and door, easily accessible from the driver-seat without having to reach.


You will have to use hose-barbs and splice a foot or so of flexible rubber line to each of the plastic lines at the electric valve, then connect them to the manual valves.


I do not trust that business of tapping a big auxillary tank into the vent or filler-tube of a factory tank;sooner or later disaster is imminent.

 

[argve]

I used a universal 6 port switching valve from Napa years ago without any problems. That way I could with a flip of the switch on the dash switch between the stock fuel system and the aux tank. no worries of ever overfilling the tanks because it operated just like a stock tank. I have talked to a few guys that installed the aux tanks as refill tanks for the stock ones and had problems with overfilling and spilling fuel out. With mine I couldn't happen because the aux tank was isolated. I think a switching valve is like 50 bucks these days from Napa... It's a solenoid operated one not like the motor driven ones on these trucks from the factory but worked just fine. Just remember to lift the fuel from the tank not pull it from the bottom... meaning that your fuel line should come up above the tank then run down under the truck. Reason for this is because the weight of the fuel will push open the switching valve and allow it to drain back into the other tanks. So just keep that in mind and you won't have a problem.

 

[MIDNIGHT RIDER]

That big military tank has most likely got a big cap/opening where you put in the fuel, like that found on big trucks.

Once you get that big tank mounted and plumbed up, it will be so quick and easy to add fuel that you will soon find yourself using the factory tanks more as "reserve" tanks and doing the most of your running on the big one; I do.

If it does have the big filler-cap, you can also use the rapid-delivery pumps around back that the big boys use, putting that sixty gallons in there quicker than you can get the nozzle threaded into those wimpy factory ones on the side.

 

[MIDNIGHT RIDER]

A LITTLE OFF TOPIC

Hey ARGVE,

I see you are from Edinburgh, or "the North end of Burton Ridge" as we call it around here.

I was just through that country twice yesterday/Sunday.


Had I have known you was that close, we would have stopped by and you could have bought our dinner.

 

[Diesel JD]

I'm not sure I understand what Travis is saying about why you have to draw from the top of the tank. Also not familiar with where the draw/return fittings on these things are. I may be installing one myself when I start making money again.

 

[RLDSL]

Here's some nice ones for hooking up 3 tanks I bought a couple of these for my truck, still need to buy hose to completely replumb the beast.

 

[MIDNIGHT RIDER]

Here's some nice ones for hooking up 3 tanks I bought a couple of these for my truck, still need to buy hose to completely replumb the beast.

Those look exactly like the ones I use, except mine are WeatherHead brand.

Look at the picture and I will attempt to describe how they are plumbed.

The port pointing straight down in the center is the OUTLET to the engine (or INLET from the engine if for a return line).

The valve is FOUR position; tank A, tank B, tank C, and OFF.

There is a sharp pointer on the handle; whichever of the three INLET ports it is pointing over is the one that is opened to the main OUTLET.

These three ports are the INLETs from the three tanks (or OUTLETs to the tanks when used on the return lines).

Each valve position has a very definite detent "click", such that it is positive as to what position the valve is turned to.


The OFF position is a very good theft deterrent, in that most thieves are not truck-drivers, so will know little about fuel-valves.

Set the valve to OFF and the engine will starve for fuel and die before they get out of the driveway.

Even if they figure out that the valve is OFF, they are still gonna be a noisy while getting the fuel to pump up and self-bleed, with the battery possibly giving up before the engine starts.


Of course, long before the truck is ever stolen, you will have run yourself out of fuel all the many times you forgot that the valve was OFF.

 

[MIDNIGHT RIDER]

I'm not sure I understand what Travis is saying about why you have to draw from the top of the tank. Also not familiar with where the draw/return fittings on these things are. I may be installing one myself when I start making money again.

The factory system draws the fuel out the top of the tank.

Many big truck tanks draw the fuel from a port at the bottom end of the tank.

When using an electric tank valve, the weight of a tank full of fuel from a bottom-draw system will "push" open the electric valve and gravity feed the fuel from the bottom-draw tank into either or both of the other tanks, possibly over-filling and running onto the ground.


Manual valves do not have this problem.

 

[franklin2]

Here's a military truck we put a dump bed on. The saddle tanks have small copper vent lines with flare fittings. These are tied together and run up front and terminate up high on the firewall for fording high water. They do have the large fill hole in the top of the tank, and I believe this gives you most of the venting while filling the tank.

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[argve]

Midnight - I actually moved the camper last weekend so... I'm now up off of 465 and 37... just down the road from the truck stops... But next time you're in the area give me a jingle...

 

[torinoracer29]

Here's a military truck we put a dump bed on. The saddle tanks have small copper vent lines with flare fittings. These are tied together and run up front and terminate up high on the firewall for fording high water. They do have the large fill hole in the top of the tank, and I believe this gives you most of the venting while filling the tank.

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The tank I have is just like the one in the picture behind the step for the door, but mine is green. I took the fuel fitting cap off and the withdraw tube picks off the bottom and the vent fitting is a rollover type vent valve, I dont think I can use this as a return line, but can I leave the return line dumping into one of the factory tanks while using the auxiliary tank. The fill cap is the big one with a strainer, the cap also has a closable vent on it for fording water. I believe I can get a vent relief fitting at my race supplier for the rollover vent on the tank. When installing the four way valves do you run rubber fuel or hard pipe it with stainless and compression fuel fittings.

 

[MIDNIGHT RIDER]

The tank I have is just like the one in the picture behind the step for the door, but mine is green. I took the fuel fitting cap off and the withdraw tube picks off the bottom and the vent fitting is a rollover type vent valve, I dont think I can use this as a return line, but can I leave the return line dumping into one of the factory tanks while using the auxiliary tank. The fill cap is the big one with a strainer, the cap also has a closable vent on it for fording water. I believe I can get a vent relief fitting at my race supplier for the rollover vent on the tank. When installing the four way valves do you run rubber fuel or hard pipe it with stainless and compression fuel fittings.

For a return-line fitting, you can just drill through the top of the tank and install a bulk-head fitting made for such purposes; they are available in NPT and JIC.

You CAN run the big tank WITHOUT a return-line, IF you are very attentive to the fuel-gauge.

I ran mine without a return for several years.

The procedure for running a big auxilliary without a return-line is :

With the big auxilliary FULL, run on one of the factory tanks that DOES HAVE a return; when that tank nears EMPTY, switch over to run on the big tank; while running on the big tank, the return is going to FILL the empty factory tank; this filling will take place a lot quicker than one would think; keep a weather eye on the gauge and, when the gauge nears FULL, switch back to the factory tank.

In normal driving, you will FILL the factory tank about 2-1/2 times from the return from a 60-gallon tank.


I used rubber fuel-line and JIC fittings on my fuel-valves.

 

[torinoracer29]

I really appreciate all the info from you guys especially you midnight. Maybe I will see a couple of you guys at the rally this year and I can thank you in person with a beer or a cocktail, then maybe you can see the finished product.