aux fuel tank in truck questions

Moved to Tech Issues forum from Towing.

I installed a pump and nozzle for mine. Pretty simple to do.

I installed RDS 50 gal tank with small tool box for LML diesel. I removed the filler neck and brazed 3/8 brass elbow. I used a ball valve then a 74 GPH transfer pump wired and loomed up to a relay switch then to a long toggle switch under the dash wired directly to a 20 amp fuse to the battery. There are gravity kits out there but I read about it over filling the tank in some cases .

What you are asking about is the basic procedure used by Transfer Flow for their in-bed tanks, of course they have a processor to control the flow and provide a guage for both tanks.

I've made two of them with my dad. 1 for a F450 he had with a 'hauler' style bed, so it was a custom fit. 1 for his 2nd gen.

The 'out' side is located on the driver's side of the tank, and pushes toward the rear of the truck along the bed side. A small nipple to a ball valve, so that the tank can be isolated because of a leak, or to remove the tank for any reason. After the ball valve there is an elbow and turns to rubber line that goes the the bed floor, and is protected using a chase-nipple (smooth radius electrical fitting). Goes through an inline fuel filter, then a 12V solenoid operated valve (aftermarket $25 fuel tank selector valve), then a high volume low pressure fuel pump. The tank is piped to a fitting that we welded to the metal part of the filler neck.

Keyed source toggle switch on dash energizes the selector valve and pump at same time to pump fuel from the aux to the main tank. Gravity feed was too slow so he added the pump.

Here is a link to the increased cost of the selector valve used. You will need to plug up one of the inlet ports (normally open port) so that junk doesn't get inside it.
Tank Selector Valve

Since you have a camper shell, here is a link to a guy that has one under a shell.
http://www.cumminsforum.com/forum/3rd-gen-non-powertrain/557689-homemade-transfer-fuel-tank-help.html#post5798574

I have a flip up side window on my topper that to fill my aux tank.