When I bought my truck it came with a auxiliary diesel mounted in the bed of the truck. It has a pump and electric fuel valve to transfer the fuel and is larger then my main fuel tank. My question is ...
I carry a 100 gallon tank in my truck. At the vent line on the main tank I spliced in a T to connect to my 100 gallon tank. I locked the cap on the truck tank and always fill into the 100 gallon tank. I have ran it this way for 4 years on gravity feed only. I never shut it off. On my 2004 GMC the gauge in the truck always shows a full tank. When the gauge starts down I look for a good fuel price.