2001 Suburban 2500 8.1L Dual Fuel Tanks Question

[jfretless]

I think I had an epiphany today while filling up my 2001 Suburban 2500 8.1L...   A few months ago I realized it has dual gas tanks and there was a pump that pumped from the rear one to the front one.  From that point, I wondered when you are filling up at the gas station, via the rear tank, as it's the only way to refill...  Does the front tank get topped off?  ...and if so, how? Since the key if out of the ignition.  So, today, I turned the key to the ACC ON, engine OFF, position and pumped gas. I was able to put 32 gallons into the truck and the LOW FUEL light wasn't even on.  If I remember correctly, I usually only get 28 gallons per fill up when the low fuel light is on.   The theory is that if the key is in the ACC ON position, the pump that transfers fuel from the rear tank to the front tank would be working and there by making more room in the rear tank as you fill it.

 

Am I crazy? 

 

Thanks.

John