2016 C@C dual tank system help

[catman3126]

Hello, I couldn't get my old login so I made a new one I'm formerly Catman3126

Okay I have 2016 C@C duramax that has the dual tank setup and he is having issue with it running out of fuel and the gauge dropping to zero randomly, does anyone have the GM Systems operation of how this system works or how its supposed to work? I need to read up on this to be able to troubleshoot it properly. it is tuned with EFI Live and I obtained the correct OS from PPEI last fall and it didn't have an issue until a couple weeks ago. he ran out of fuel at 248 miles, air coming out of the bleeder along side of the road and had it towed to the dealer. they got it going and said everything was working correctly but its not and the fuel gauge dropped to zero this AM but he was not able to put any fuel in the front tank and the tank took 21 gallons which is about what front tank capacity is. from what we have read the system is supposed to keep both tanks at similar levels but we have not found a definitive answer on this either and the dealer in town was not able to explain how the system actually works. any help is greatly appreciated.

 

[Chevy1925]

Hello, I couldn't get my old login so I made a new one I'm formerly Catman3126

Okay I have 2016 C@C duramax that has the dual tank setup and he is having issue with it running out of fuel and the gauge dropping to zero randomly, does anyone have the GM Systems operation of how this system works or how its supposed to work? I need to read up on this to be able to troubleshoot it properly. it is tuned with EFI Live and I obtained the correct OS from PPEI last fall and it didn't have an issue until a couple weeks ago. he ran out of fuel at 248 miles, air coming out of the bleeder along side of the road and had it towed to the dealer. they got it going and said everything was working correctly but its not and the fuel gauge dropped to zero this AM but he was not able to put any fuel in the front tank and the tank took 21 gallons which is about what front tank capacity is. from what we have read the system is supposed to keep both tanks at similar levels but we have not found a definitive answer on this either and the dealer in town was not able to explain how the system actually works. any help is greatly appreciated.

Pm me what its doing, why you cant log in. we will fix it

 

[JoshH]

Cab and chassis trucks have a transfer pump that pumps fuel from the rear tank into the front tank depending on fuel levels reported by the sending unit in each tank which sets priority for maintaining fuel in the front tank. Those pumps are pretty bad about going out. I would look into that and make sure both sending units are working properly.

Edit: I just looked up the info on how it operates the transfer pump just to make sure. The pump turns on when the front tank is less than 16.9 gallons and the rear tank is more than 2.6 gallons. The pump shuts off when the front tank reaches 20.9 gallons. This cycle continues until the rear tank drops below 2.6 gallons. Once the rear tank is below 2.6 gallons and the front tank is below 20.9 gallons, the pump is turned on for 300 seconds to pump all remaining fuel into the front tank.

 

[catman3126]

Pm me what its doing, why you cant log in. we will fix it

I described exactly whats it doing in my post, I did the email for my other login and never received the recovery email so I logged in with this username, I'm not concerned with the other login at this time just wanting info on how that dual tank system works. thanks

 

[catman3126]

Cab and chassis trucks have a transfer pump that pumps fuel from the rear tank into the front tank depending on fuel levels reported by the sending unit in each tank which sets priority for maintaining fuel in the front tank. Those pumps are pretty bad about going out. I would look into that and make sure both sending units are working properly.

Does it keep the front tank topped off or does it keep it at a middle of the road level? what sender the fuel gauge in the dash read from? the rear pump is working as the dealer was able to turn it on with their scan tool, so if the gauge is doing weird things randomly which sender is it? front tank?

 

[Bdsankey]

Does it keep the front tank topped off or does it keep it at a middle of the road level? what sender the fuel gauge in the dash read from? the rear pump is working as the dealer was able to turn it on with their scan tool, so if the gauge is doing weird things randomly which sender is it? front tank?

See Josh's edit, it should answer your question.

 

[DPC]

Recall #17067

Sounds like your problem

#17067: Product Emissions Recall - Diesel Dual Tank Fuel Transfer Pump Plumbing & Diagnostics - (May 1, 2018)
Subject:
17067 — Diesel Dual Tank Fuel Transfer Pump Plumbing & Diagnostics

Models:
2015–2016 Chevrolet Silverado HD
2015–2016 GMC Sierra HD

General Motors has decided to conduct a Voluntary Emission Recall on certain 2015-2016 model year Chevrolet Silverado HD and GMC Sierra HD vehicles equipped with a 6.6L diesel (LML) engine and dual fuel tanks (N2N). Under certain driving conditions, fuel may not be transferred from the rear fuel tank to the front fuel tank at a sufficient rate. If this occurs, the diagnostic trouble code (DTC) P2636 will set, the malfunction indicator lamp will illuminate, the fuel gauge will display empty, and the transfer pump will be disabled until serviced. If the vehicle continues to be driven, it will run out of fuel in the front tank and stall.

 

[MarkBroviak]

There is also an issue with the float arm catching the filler tube in the front tank iirc and causing a big issue as well with these trucks. Had a dealer send me a picture of this issue after a long battle with this same issue.

 

[catman3126]

It also has code P0463 that just popped up two days ago.

 

[2009Loren]

Did you ever get this resolved? I’m having the same issue.

 

[autotech6506]

I have a truck that is setting code p2636 for insufficent flow as well. It already has the update kit installed and has been running without a problem for the last two years. All of a sudden it is setting the code again. I have examined the feed line to make surenit is not kinked and the breather is open on rear tank. Pump runs when commanded but i suspect it is not really pumping anything. I am going to order a transfer pump for it. Looks just like a lift pump for the old 6.5 chevy turbo diesels. I will report back when I get it installed.