Need advice

Anyone plumbed an in bed tank into their existing factory tank with out paying big bucks for some computer controlled pump? I have found one that advertises it will gravity feed into your lower tank without overflowing it, I believe RDS makes it? Has anyone used one with success?

I have thought of using an electric solenoid valve but all of them state they need some pressure to fully open or close properly. I would prefer to not have to hop out and open a manual ball valve either.

Ball valve, 5/8" line threw small hole in corner of bed, welded bung on filler neck and screw in barbed fitting for above mentioned line...done...

Transfer flow 3/8 line through hole in bed into gas door into filler neck with light up switch on dash so can also refuel other tools/Equiptment also

Mine is piped into the sending unit cover, thru a bulkhead fitting. Swagelok stainless fittings, all 1/2", cause they were free, lol.
Anyway, I used a push lock adaptor with about a foot of hose between the oem tank and the extra tank, for flexibility.
On the bed mounted tank, once again, 1/2" ss fittings, a standard ball vlv, and a 3/4" solenoid vlv. I stepped the solenoid vlv up in size to keep the flow rate a little higher, and it was only about 10$ more. I tried a 1/2" vlv, just took too long to gravity feed when the extra tank got low i.e. very little head pressure.
To run the solenoid vlv, I mounted a lighted switch in the dash, and I just watch the oem gauge, when it gets to the full mark, turn it off. It takes about 25 minutes to fill from a qtr tank to full, when the auxiliary tank is full, and about 35 minutes when the auxiliary tank is about empty. So, not fast by any means, but when you've got 1200 miles to go, who cares, lol.
I pulled power for the solenoid from my fuel pump harness, however, I have a dual fuel pump setup, with relays, and big wire from the batteries. I can't remember the amp draw for the solenoid vlv off hand, but seems like it would have been a little much forthe stock wiring.
I tried a redhead solenoid vlv originally, however, as the op mentioned, they require a pressure differential to work effectively. I Googled "ss solenoid vlv", and "solenoid vlv", and found a company that sells a few different brands of vlvs, several of which don't need a pressure differential to work. Think mine cost about 80$, and has a brass body.

To add, I think a guy could build this setup, or similar, with different materials maybe, for a couple hundred, plus the tank, of course. Mine is ss just because I had the material available, no other reason.

This was originally piped into the filler neck as blk99 mentioned, but I thought that method could use a little refinement, lol.
The biggest improvement was wiring the solenoid into the fuel pump harness, so the vlv closes when you turn the key off. Otherwise, it'll keep on draining the auxiliary tank to the oem tank, and eventually, on to the ground. Ask me how I know.:fustrate:
Once of doing that, and you've paid for a fuel transfer system, lol.
Obviously, all this works as long as you can give up bed space, if you want to mount the auxiliary tank under the bed, you'll need to add a pump to the equation.

Where did you source the 12v solenoid?

Stcvavle