Saddle Tanks, Dual Fill.

[Tucson38]

Mr. Newbie here. Hello to everyone.
'85 GMC 4 WD HD 3/4 - 252,000 miles. Original owner.

I'd sure like to bypass the switching device GM uses. Seems way more problematic than necessary. I'd opt for using one filler neck for both tanks.

[Pyrotechnic]

DirtyLarry came up with an idea I really liked. He was having trouble using the solenoid switching valve with a high pressure fuel injection pump, so he ditched the valve all together. Instead, one tank is the primary with the fuel pump send and return plumbed to it. The other tank has an electric transfer pump that will fill the primary tank.

This is the route I plan to go on my truck. If you have a nice transfer pump, I bet you could fill your secondary, transfer that fuel to the other side, then refill the secondary all without moving the truck. Might take a few extra minutes, but you'd be really surprised how fast a good electric pump can move a gallon of gas at free flow.

[68 TT]

Originally Posted by Pyrotechnic

DirtyLarry came up with an idea I really liked. He was having trouble using the solenoid switching valve with a high pressure fuel injection pump, so he ditched the valve all together. Instead, one tank is the primary with the fuel pump send and return plumbed to it. The other tank has an electric transfer pump that will fill the primary tank.

This is the route I plan to go on my truck. If you have a nice transfer pump, I bet you could fill your secondary, transfer that fuel to the other side, then refill the secondary all without moving the truck. Might take a few extra minutes, but you'd be really surprised how fast a good electric pump can move a gallon of gas at free flow.

A high flow 255 LPH EFI pump would take almost 18 minutes to drain a 20 gallon tank. Even my 110 GPH Holley race pump would take almost 11 minutes to transfer 20 gallons. It would be fine for a transfer pump while driving but wouldn't save you any time filling tanks.

It needs to have some type of sensor to shut it off when the tank is dry so you don't burn it out. Just a toggle switch could work but you would have to keep a close eye on it and listen for the pump to start cavitation then shut it off. It wouldn't take long to kill the pump running it dry.