Can someone explain the dual fuel tank set up I have?

[Nicolai8775]

Hey all, after blowing up my transfer case due to pump rub and subsequently running dry.. I realized while I was under the truck that I have dual fuel tanks.

My truck is a 2001 Chevy Suburban 2500 6.0.

Can anyone explain how it works, the capacity of the main tank vs smaller tank, etc. I assume when I fill up gas it fills up the smaller tank then trickles to the larger tank. Is there a pump in the smaller tank? I was chasing a P0300, where I did a fuel leak down test and noticed it dropped about 20psi after 45 minutes. Over night it would drop to zero. I believe I have fixed that issue but don't want to leave anything to chance. Is there one of those check valves in the auxiliary tank pump? Does it even have a pump?

 

[swathdiver]

Hey all, after blowing up my transfer case due to pump rub and subsequently running dry.. I realized while I was under the truck that I have dual fuel tanks.

My truck is a 2001 Chevy Suburban 2500 6.0.

Can anyone explain how it works, the capacity of the main tank vs smaller tank, etc. I assume when I fill up gas it fills up the smaller tank then trickles to the larger tank. Is there a pump in the smaller tank? I was chasing a P0300, where I did a fuel leak down test and noticed it dropped about 20psi after 45 minutes. Over night it would drop to zero. I believe I have fixed that issue but don't want to leave anything to chance. Is there one of those check valves in the auxiliary tank pump? Does it even have a pump?

Front tank is 26 gallons, rear tank is 11.4 gallons.





GMT900 uses the same rear fuel tank, not sure about the pumps though.

 

[Nicolai8775]

Front tank is 26 gallons, rear tank is 11.4 gallons.

View attachment 366491
View attachment 366492
View attachment 366493

GMT900 uses the same rear fuel tank, not sure about the pumps though.

This is so cool. And far more advanced than the old k10 I used to have with dual tanks.

 

[Nicolai8775]

Ok so for anyone wondering. I was curious as to when the secondary pump kicked in. I found an old forum post on gm-trucks. A guy wired a light into his dash attached to the secondary pump circuit. It appeared to turn on at 2/3s tank for about 5 minutes. Then it would continue to turn on in short intervals between 2/3s tank to 1/2tank until the aux tank was empty. I read this system is prone to "slow fill ups" and is often disconnected. I'm gonna have to pay attention this tank to see how many miles I get per tank. It seems low so I'm wondering if the aux tank only fills main take with gravity until it can't anymore and there's always fuel left in the bottom of the aux tank. Or it had the slow fill up problem and they took out the relay.

 

[S33k3r]

There are two pumps. Pump gas goes into the smaller tank first, then into the main tank. Gas guage is calibrated to total gas available.

 

[S33k3r]

Ok so for anyone wondering. I was curious as to when the secondary pump kicked in. I found an old forum post on gm-trucks. A guy wired a light into his dash attached to the secondary pump circuit. It appeared to turn on at 2/3s tank for about 5 minutes. Then it would continue to turn on in short intervals between 2/3s tank to 1/2tank until the aux tank was empty. I read this system is prone to "slow fill ups" and is often disconnected. I'm gonna have to pay attention this tank to see how many miles I get per tank. It seems low so I'm wondering if the aux tank only fills main take with gravity until it can't anymore and there's always fuel left in the bottom of the aux tank. Or it had the slow fill up problem and they took out the relay.

I believe both tanks try to maintain a reserve because both use gasoline for cooling/lubricant.

 

[S33k3r]

This is a little more information, but does not explain when the pumps kick in, sorry.

Did You Know That Some Suburban’s Have Two Fuel Pumps?