Dual fuel tank install

[rustystud]

View attachment Scan0014.pdfView attachment Scan0015.pdf Here are the diagrams for the electrical and fuel lines I promised. Sorry about the quality, I am not a draftsman. If anyone has questions just ask.

 

[gringeltaube]

... One thing I didn't want to do was use the change over switch that my Chevy uses like your switch. I wanted threaded fittings so I could use PTFE hose. The problem was no ones makes this switch in a metal design that uses NPT threads. At least none that I could afford ! So since I would be using 2 fuel pumps I was able to use the one-way check valves as my switching device. Just cut off the power to one pump and energize the other. The real problem was finding a good 3 way fuel switch for the return lines. I got mine on eBay for $80.00 .

Well, I mentioned that combined 6-way switch as an option and really only used it once (for a MB-diesel/SVO powered Jeep). I do prefer threaded fittings, also.
This is what I used for the fuel return: two solenoid valves - everything having NPT threads and sealed with Loctite 518.
Note the extra pressure relief valve on top of the filter housing.



G.

 

[Jeepsinker]

Hey Garrett speaking about transmissions, how is the front seal mod going ? Before I finish the transmission I want to install this input shaft support unit. Being able to fill the transmission to it's proper level will increase bearing life and synchro's too.
Thanks.

All the way to the rally and back, plus a couple hundred miles, and still dry as a bone! Somewhere real close to 2000 miles on it already.

 

[Tracer]

I decided this would be best for my "Grand Alaskan Expedition" with my son. I will also be adding about ten 5 gallon fuel cans to be carried in the trailer. Either that or a large fuel tank with transfer pump.

Rusty, for your second fuel tank, are you using the fuel tank from an M275A2?

 

[rustystud]

Rusty, for your second fuel tank, are you using the fuel tank from an M275A2?

No, it's from another M35A2 truck.

 

[rustystud]

Well, I mentioned that combined 6-way switch as an option and really only used it once (for a MB-diesel/SVO powered Jeep). I do prefer threaded fittings, also.
This is what I used for the fuel return: two solenoid valves - everything having NPT threads and sealed with Loctite 518.
Note the extra pressure relief valve on top of the filter housing.



G.

Going your way with the two solenoids probably would have been cheaper then going with the one 3 way valve. That valve cost me $80.00 .

 

[Tracer]

No, it's from another M35A2 truck.

Rusty, I'm sure you have been down this road, but would it be possible to use an M275A2 fuel tank? And in doing so, would I have to give up my tool box, spare tire, and pioneer rack?

 

[rustystud]

Rusty, I'm sure you have been down this road, but would it be possible to use an M275A2 fuel tank? And in doing so, would I have to give up my tool box, spare tire, and pioneer rack?

There's no way to fit any of that stuff if your going with a second fuel tank. The only thing that you get to keep is the tool box.

 

[rustystud]

I found a picture of the 3 way valve and the one-way check valves. These two items and the switch (not pictured) are what really make the system work.

 

[Wildchild467]

Really?

You're my hero Hahaha

 

[rustystud]

Really?

Actually your system is "not" a dual tank system. You still only have "one" tank just divided.
We have to be accurate here Gerhard.
Also, did you have a switchable fuel level system like mine for the fuel gauge ? I couldn't see one in your post.

 

[Jeepsinker]

Rusty, I have to ask... why didn't you just plumb it so the second tank pumps into the first?

 

[rustystud]

Rusty, I have to ask... why didn't you just plumb it so the second tank pumps into the first?

Just in case I got a bad tank of fuel (which has happened to me) I wanted some insurance that I could still drive it.
The way I drive all my vehicles is I always fill-up at half a tank full. So when driving my dual tank deuce, when one tank gets close to empty I will fill it up and continue driving down the road using the other tank till it gets close to empty. So you never know what kind of fuel will be in one tank since it is coming from a different fuel station. At one fuel station in eastern Washington they must have been nearly on empty tanks and the stuff that got in my fuel tank was mostly water and other crap. I only got about 5 miles away before my truck started to act like a raped ape ! Thankfully I always fill up at half a tank, so after draining a lot of fuel out and adding good fuel back in I was able to limp it back home.

 

[gringeltaube]

Actually your system is "not" a dual tank system. You still only have "one" tank just divided.
We have to be accurate here Gerhard.
Also, did you have a switchable fuel level system like mine for the fuel gauge ? I couldn't see one in your post.

1) Two independent systems, one main - one auxiliary, just for the cold start period - and to be able to "flush" the IP before any longer stop. Germans call that a "Zwei-Tank-System" - even if the two tanks were siamesed.
2) Two floats/sending units - one fuel gauge. And yes, it's all controlled by that one switch.



That was my first SVO-conversion, back then. In all these years I have done a few more - with some improvements like using aluminum instead of copper, for the heating coil.





I never felt that this particular conversion was something worth posting much, since most people here don't burn other than WMO - or mixtures of the same with diesel/gas and simply adjusting the viscosity by more or less diluting the "dense" stuff. No need to
preheat fuel, in most cases.


G.

 

[rustystud]

As far as calling your system a "dual tank" system, I guess if your in Germany that's OK, but we are here in the U.S.A. and my system really does have "two" separate tanks ! LOL
To bad you never posted "all" that you did to your system. It would have helped me when I was figuring out mine.
Now if you had posted everything back then (I remember reading it) I wouldn't have said mine was the "only" one with just a one switch system.

 

[emeralcove]

I have done nothing more on my "dual tank" system than mounting the second tank. I was thinking along the same lines as you with the check valves, but you have gone further with filters and gauges. Do you have a "plumbing schematic" indicating how and where you placed the check valves, filters gauges etc.? I have also been considering adding a transfer pump from one side to another as an additional layer of redundancy.

 

[rmgill]

Given how the fuel system doesn't need the in tank pump to lift fuel to the IP, how are you not picking up some fuel from the non-selected tank?

 

[rustystud]

I have done nothing more on my "dual tank" system than mounting the second tank. I was thinking along the same lines as you with the check valves, but you have gone further with filters and gauges. Do you have a "plumbing schematic" indicating how and where you placed the check valves, filters gauges etc.? I have also been considering adding a transfer pump from one side to another as an additional layer of redundancy.

I put that back on post 21. Both diagrams, one electrical and the other the plumbing.

 

[rustystud]

Given how the fuel system doesn't need the in tank pump to lift fuel to the IP, how are you not picking up some fuel from the non-selected tank?

Since each tank has a pump, when one is in operation it forces the other tanks one-way check valve closed. There is no way any fuel is coming out of the non-used line.

 

[rustystud]

As far as calling your system a "dual tank" system, I guess if your in Germany that's OK, but we are here in the U.S.A. and my system really does have "two" separate tanks ! LOL
To bad you never posted "all" that you did to your system. It would have helped me when I was figuring out mine.
Now if you had posted everything back then (I remember reading it) I wouldn't have said mine was the "only" one with just a one switch system.

Gerhard, I owe you an apology. After reading this thread again I see that my responses to you where very abrupt and came across as not very friendly. That was not my intention at all. The only explanation I can give for my rude behavior is due to the medication I'm on. Usually my wife will let me know when I'm being an A$$hole but she doesn't read this site. Your idea of a dual tank system was the same as mine and very well done. I do wish that you had posted it years ago though. It would have saved me some money and time.