Be careful about removing the rear tank, the ecm monitors the fuel level in the rear tank and front tank to determine when to run the transfer pump. When my rear tank sensor went out, the ecm determined I was out of fuel and shut down the engine. You might be able to fool the ecm into thinking your reserve tank is the second tank.

 

I thought some trucks only came with one main tank?
Wonder if my dealer could flash my ecu and eliminate that second tank pump?

 

Never mind, buddy at dealer said can't go in there and delete that second tank.
He said both tanks will even them selves out, so he said even if you only fill the main tank full and never fill the back it will eventually even out and show half a tank of diesel on your fuel guage.

 

probably why it works to connect an auxiliary tank to the front tank only. ?

 

Yes, was told leave rear tank, and hook transfer tank to main tank.

 

I have never tried this but I do not know why this would not work.

In EFI Live there is a setting for fuel system. Under that is the configuration for the whole fuel system. This tells the system what size the main tank is and what to total fuel system capacity is.

So the main fuel tank size stays the same. The total capacity would change to main size + new tank size.

The Fuel Level Sensor Primary would also stay the same.

The Fuel Level Sensor Secondary would change, in the screen shown the tank size is 15 gallons. I would think you would set it all to 0 Volts. This would make the system think is empty.

A better plan would be to set it to use the level sensor in the new secondary tank. You would then need to do some testing. I would monitor the level sensor PID (GM.FUELLVLRS) with EFI Live as you slowly added fuel to the new secondary tank until it was full, taking notes on how many gallon at each level in the list. Connect the new tank to the factory transfer pump. In theory it should act as the original tank including the factory gas gauge.

After all that being said, who's going to be the guinea pig?

 

speaking of fuel tanks, is there a reason that diesel pumps at the stations, including the truck stops, never shut off till it spills fuel all over the side of the truck? The gas pumps seem to be able to sense when to shut off properly, but not diesel.

 

Guess on my part but fill nosles use a venture effect to sense when the tank is getting full. Since diesel foams really bad I assume the venture has a hard time sensing the pressure difference because of the foam. By the time it does there is a lot of foam and it bealches out. I can usually add another 2-5 gallons after the bealch to get it full.