2000 Chev 3500 Factory Inline Rear Tank Fuel Pump

[67JimmyMO]

I was hoping someone could explain to me how the inline fuel pump between the front and rear fuel tanks works on a 2000 Chev 3500 chassis/cab.

It is the 159.5" wheelbase with 454 Vortec.

There is no switch on the dash to switch between tanks so I guess that the inline pump is triggered automatically somehow, and then transfers fuel from the back tank to the front tank?

Also wondering what tank the fuel gauge is reading, I am assuming that it reads the level of the front tank?

A little background...when I purchased the truck in 2015 the previous owner told me to consider the truck empty when the fuel gauge read 1/4 full, and I have always done that. Well last week I ran out of gas with the gauge reading 3/8 full. I poured 5 gallons into the front tank and got it going again, but when I got to the gas station the rear tank was totally full.

I have attached a pic of the truck and a link to the inline pump, thanks for any info you can give me on this.

https://www.ebay.com/itm/BRAND-NEW-F...53.m1438.l2649