Second fuel tank automatic switching.....

[GeneralDisorder]

Thinking of using one of these for switching fuel supply and return. I have a second FMTV tank and brackets to go behind the primary.

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[AKPacker]

Haha wow, I was just looking into these myself for the second tank I recently pulled from a parts truck. Our two trucks are going to wind up with a lot of parallels. I've been waffling between manual valves for reliability, and electronic valves for convenience/the ability to switch tanks on the go from the cab.

 

[GeneralDisorder]

Manual valve would be my preference on a non tilt cab truck. The classic six-way brass lever valve.... Not convenient with our trucks - I'm not running six damn fuel lines up through the cab pivot interface....

Not too concerned with reliability. This being a hydraulic cylinder control valve it should handle WAY more pressure than our fuel delivery system. And in any case of it fails you can just swap the lines and suck fuel through the side of the valve that is connected in whatever state it fails in.

I want the tanks separate for redundancy (in case one is punctured, etc) and for frame flex concerns on some of these huge long tanks that guys run. Seems like a stupid idea to me. And the fuel sloshes away from the pickup in the center so your effective capacity is reduced as you approach an empty tank. A solenoid valve potential failure point is a worthwhile trade off to me for not dealing with the large single tank drawbacks.

 

[Ronmar]

As long as the valve can handle suction, many hydraulic valves are not very good at it...

Have always liked the buddy tank concept as it keeps the fuel system to a dedicated tank and no valves. The main tank is vented thru the secondary tank and a basic lift pump transfers fuel from secondary to main. Can be on a timer or even a float switch in the main tank to control the feed pump and any possible overfill will simply return to the buddy tank via the vent line... This of course doesn't help with tank damage but it is simple...

 

[coachgeo]

for manual valve in a tilt cab.... mount it on a plate X"xY" large.. cut hole in floor of cab.. that is that minus a bit... but not minus so much the valves dont fit thru hole in cab floor. Put a seal on the plate that squashes as the cab closes. then again you have to accommodate for flexing too since cab is on shocks and possible mount surfaces below cab are not on shocks. (Engine and it's accessories) hmmmm...

 

[Suprman]

Put the manual valve by the tanks and just get out and switch it over when you need to. I have the manual valves from m939 trucks.

 

[AKPacker]

@GeneralDisorder what is you plan for gauging the second tank? I was planning to add a second stock gauge in the "empty" spot on the dash next to the original gauge, but since the A1R gauges go through the MMDC it isn't as straightforward as I'd hoped.

 

[Ronmar]

Well you could probably add a second sender and switch between that and the main gauge sender input to the MMDC…

 

[simp5782]

I ran a 12v inline pump thru a filter head on my 920 so all the fuel from the auxiliary tank was filtered down to 2 micron before filling the main tank back up in about 10mins. Just was easier on my main filters on the motor that were 10 micron

 

[Ronmar]

I ran a 12v inline pump thru a filter head on my 920 so all the fuel from the auxiliary tank was filtered down to 2 micron before filling the main tank back up in about 10mins. Just was easier on my main filters on the motor that were 10 micron

I have done fuel systems like this in the past, simple, no valves easy to remote control.

 

[simp5782]

I have done fuel systems like this in the past, simple, no valves easy to remote control.

I had a setup where the bottom of the tank drains had a line that connected to the other tank via the drain but it was just too exposed without a cross member that low to getting hit by road debris. Most semis use it but they are so low to the ground already hard for stuff to go smooth underneath em

 

[Ronmar]

I had a setup where the bottom of the tank drains had a like that connected to the other tank via the drain but it was just too exposed without a cross member that low to getting hit by road debris. Most semis use it but they are so low to the ground already hard for stuff to go smooth underneath em

Yep, I had one in an old Toyota like that, gravity only, the filler pipes were tied together so only one filler port. Had 8.5 hours of fuel at highway speed. Yes the lower crossover hose was exposed.

what I and others are proposing is an upper crossover using a pump. You vent the main tank thru the secondary/aux tank and you install an electric feed pump to move fuel from the aux tank to the main tank at the flip of a switch as needed(even perhaps adding a timer). But if it does overfill, any excess in the main tank would flow back thru the main vent to the aux tank… a second sender and a switch, or a second fuel gauge would be handy to keep track of Aux fuel…