Does anyone here know how GM sets up their dual fuel tank systems? I tuned a 07 LBZ with the 6698 cal for better mileage and a little power. It came with dual tanks under the flatbed and now the owner states that his fuel does not transfer from the second tank anymore. I compared back to the original and can find nothing that has been changed with any of the fuel tank settings.
I don't see an option for any factory fuel transferring. Ideas, anyone?

I am guessing that they use the same type valve as used on the older gas trucks with dual tanks. It is a 3 port valve- one end goes to each tank and third port will feed the engine. It has a small solenoid inside that switches to which side it will draw fuel from. With NO power to the solenoid, it will default to one tank. With power, it will switch sides and draw fuel from the other tank. (some have six ports to switch the return fuel back to the correct tank at the same time)

Your problem may be a bad fuse, a stuck solenoid, plugged port, or defective solenoid. You need to find the switching valve (probably close to the tanks) and test for power to the valve when the other tank is selected. If it has power and a good ground, the valve probably needs replaced.

I am guessing that this vehicle uses this type valve!

you built the tune from his stock tune?

try relfashing back to stock and see if it will cure his problom?

I can't see how it would effect it but...............

you built the tune from his stock tune?

try relfashing back to stock and see if it will cure his problom?

I can't see how it would effect it but...............

Yes, I built it from his stock tune, tried his original back in, but it didn't help.
Makes no sense to me.

Yes, I built it from his stock tune, tried his original back in, but it didn't help.
Makes no sense to me.

Well if his truck won't switch tanks with his stock tune loaded in, its probably not efilive related. Like stated above, a bad fuse or valve or something else is more than likely the culprit.

Well if his truck won't switch tanks with his stock tune loaded in, its probably not efilive related. Like stated above, a bad fuse or valve or something else is more than likely the culprit.


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