The latest-greatest- plan here is to use the RDS fuel neck kit with an aux tank under the toolbox, but I'm not sure of several things:

* Anyone know of a specific filter/water separator that would work with a gravity feed aux tank? I could get a pair of in-line filter heads and screw on filters like if it were a transfer tank, but at those going to be too restrictive without a pump?

* How close to bed/tank outlet level does that kit put the valve in the fuel neck? Presumably it's lower since gravity feed doesn't run uphill and RDS says this works, but I don't want the bottom two inches of the aux tank to not drain since this thing is pretty flat and that would waste 20-30% of the tank capacity.

* Is gravity going to get the fuel through a filter (mounted to the frame? Where else?) without a pump quickly enough to be useful, especially towards the end of the tank?

* Worth putting a solenoid in the line at the tank? Run that off an Aux switch from the cab. Then have a manual ball valve on the filter?

 

We just run our 95 gal tanks with a ball valve right at the tank then gravity fed to the trucks filler neck,the trucks filtering system has done us well in 4-5 trucks over 300k miles each,we know when time to fill by our dash gauge,we have maybe 2-3 gal left in aux tank on fillups.

 

How fast are you running through the aux tanks? I'm setting this up to slide it in when I need it and pull it when I don't, so I was thinking filter setup versus flushing the tank out every use? I'll drain the tank when I pull it, but it'll sit empty in the barn more often than there's diesel in it so I was worried about crap getting in or building up in it.

 

when in storage i guess you could cap the tank vents so no dirt dobbers get in, i use mine fast so not worried about that.

 

My father and I both have the RDS 91 gallon tool/fuel box. We leave them in. On both we use electric pumps and an in line see thru gas style filter. Both are wired off the up-fitter switches. Both draw fuel from the top center fitting that has an inline 1/4 turn valve.
Now here's the difference. He mounted his pump and filter up top inside the tool box. He ran the power/ground feed and fuel lines through grommets to the inside of the box. So in essence to remove the tank he has to unplug the electrical plug and undo one fuel line that goes through the stake pocket to the filler neck.
On mine I mounted the pump and filter down on the frame. Mine, once primed, was gravity feeding when I didn't want it too so I added an electric solinoid valve that I found on Amazon. The valve only opens when powered and holds back head pressure when it is off. Been working fine for years. If I want to remove my tank it's only one hose and it's out.
I'd highly recommend using a solinoid and pump. The gravity feed idea can get you jammed up when you go out in the morning and see a puddle of fuel on the ground because you forgot to turn off the valve the night before. Or the sheen left on your paint when it's dripping out while going down the road.
​​You can assume how I know.

 

I forgot to mention we had to modify all trucks with aux gravity feeds truck cap so no leaks after sitting since all tanks are vented in the aux tank per dot/fmcsa,i did have one truck that lost overnite but none after fixing the cap, i forgot till 87crew mentioned that,memory needs reflashed.

 

Thanks for the advice, got specific parts recommendations?

Which cap did you fix and how? The fuel cap on the truck or the vent cap on the tank? Looks the RDS tanks have a rollover valve that you can run the vent line up from? Thans

 

cap on the truck,it has a built in vent that allows fuel to run out sometimes with gravity feed systems,also theres a rollover valve on the trucks tanks,sometimes if you run your truck tank down then fill the aux tank, fuel will drip out that overflow hose untill enough pressure against the ball to seal the trucks rollover hose,all dot aproved aux tanks have a rollover/vent.The short hose on the trucks tank cant be plugged per dot,mine will drip for about 5 mins if the scenario plays out,soon as enough fuel against it no more drip.Ive never run a pump so i dont know if that happens or not with one.Also my aux tank has a place to put a ball valve at the very bottom driver side so it drain about all out i guess while going around curves if that low or if truck leans that side.

 

Ah makes sense, thanks. Anyone know where the tank vent line terminates? Hose barb and run it up the front of the bed? Won't have to get very high to get over my tank since it'll be under the box.

 

https://www.ford-trucks.com/forums/1...nk-vented.html looks like some have two vents,one front of tank top,one on rear.

 

One thought on a tank just out sitting.
Algae.

 

Parts arriving today hopefully. Maybe a dumb question but:

I want to check the flow of this set up, so is it a problem to fill the aux tank with a mostly empty truck tank?

Some people mention air locks in the gravity feed line. Since this is under the toolbox and I can't reach a manual valve I'm going to put a solenoid valve on the tank, any concern of air locking with an empty truck tank and a full aux tank?

I know I'm overthinking, I'll just do it

Only thing I'm really confused on is I looked at it this morning and looks like I have to cut off part of the hard line to put the fill neck adapter in? There's only a couple inches of rubber hose outside the frame rail. I'm guessing I have to cut the rubber line and remove, then cut the hard pipe, then splice together? Maybe when I have the part in-hand it'll look to fit better.

 

i used all brass fittings i had here so not sure what youll get,best i remember ours go thru the 3/4 hose thats right with the trucks fill hose,i leave valve open all the time so not sure how long it takes realy to refill the truck tank,im thinking 15-20 mins if empty,did you modify your trucks fuel cap? are you wanting to leave valve open all the time or just open when you need fuel,you may not need to modify the cap.

 

I too used all brass fitting and T'ed in on the factory vent hose. You can also see the Facet pump and the yellow & blue wires are for the normallu closed solenoid.

 

Haven't modified the cap yet. Truck use pattern is basically heavy-off awhile-heavy-off awhile (no lectures on it sitting please ), so I'm thinking I'm going to close the valve most of the time so fuel doesn't just sit there pushing on the truck's cap. Drive the truck until it's about half down in the main tank (3/4 - 1/2 on the main gauge), then open the valve and refill the aux tank to keep the fuel fresh in it.