I've obtained a 90-gallon in-bed aux tank and want to set it up to gravity feed into my OEM filler neck. Can anyone tell me what I need to do to install my RDS transfer kit to my front tank fill line? I was looking at it and realized that I can't just cut the filler neck and install it with hose clamps since there is a rubber hose running inside the steel filler pipe. Is there no way to set up this gravity-feed aux line so that it fills through the OEM filler neck? Is there some other kit I need instead of the RDS #011025?

I can weld in a fitting directly to the steel filler that the aux fill valve will screw into but then I need to figure out a way to move the inner rubber hose back in to place such that diesel would still flow into the tank and not all over everything.
I'd love to get this thing right and have significantly more capacity. Thanks for any help!!

 

I found a solution to my dilemma. I drilled a hole into the steel filler neck, welded a fitting on, then screwed in the automatic gravity fill valve, then reinstalled everything.

 

Here is the finished product:

If anyone can see anything wrong with this then please let me know. I had the guys at work help me get this done.

 

wont that will make the tank too full? if the fuel is cold and warms up during the day it will expand. where will it go?

 

Looks fine to me. Does the RDS system you speak of trigger fill by level control and fill till full or is it a manual transfer? Does it have a hi hi shutoff switch? How does it work?

Diesel has such a high flash point you do not need to worry about thermal vapor release, unless you get fuel in ND at -40 and then figure out how to get to get to Cabo with a topped off ice cold tank at 120 degrees ambient :-)


When I fuel up I fill the truck to the top of both filler neck, never had an issue, nor do I expect to.

 

What I did after doing the vent mod was to put a hole in the rubber hose and insert a plastic small hose into the big rubber hose just enough to get it in there. I then used marine tex around the outside to stop any leaks. In the bed I drill a small hole, ran this line thru to a small transfer pump. Between the pump and my aux tank I installed a electric check valve. Inside the cab I have a toggle switch so when I flip it power is supplied to the pump and check valve. It will fill my tank a little faster then I can use it when driving so I watch the tank fill. This is not a professional install but works great, I have been using it for years. Got the pump at NAPA. When I first installed it I didn't realize the gravity flow and was greeted by a puddle of fuel on the ground the next day, LOL

 

I am going to want to check this out in more detail at rre.... I really like the idea of an in bed tank with a toggled pump...

 

NO! you can't look at it Lee, LOL

 

Sorry for the delay... Anyway, it is gravity-fed and in the brass piece there is a hollow metal ball check that will "float" backwards if the fuel level gets high enough in the filler neck. That is what screws into the welded piece. Also, there is a block valve in the tank outlet in the bed that I can block (it is currently) and open for, say, a long-haul trip where I'm pulling a load and will use more fuel.