Any way to delete front fuel tank on chassis cab?

[samuse]

I have a ‘17 chassis cab 3500 6.0 gas with dual tanks that have been driving me nuts.  
 

The guage won’t work and it is not, or not all the time, pumping fuel from the rear tank to the front. 
 

This truck pulls a lot so it’s usually getting 5-5-5 mpg and 100 mile range with no fuel gauge is just not acceptable. 
 

The 40 gallon tank on its own with a working fuel gauge would be plenty acceptable.  
 

Truck has 14K (yeah 14) and is in new condition otherwise.  

[newdude]

The front tank is the primary, so the engine is fed off of that.  

 

The rear tank is the secondary and just supplies the primary.  

 

I'd suggest fixing the issue with your fuel gauge.

[samuse]

3 hours ago, newdude said:

The front tank is the primary, so the engine is fed off of that.  

 

The rear tank is the secondary and just supplies the primary.  

 

I'd suggest fixing the issue with your fuel gauge.

It’s not just the gauge. The gauge is always at 1/4 but it’s also not pumping from the rear tank sometimes so I might go 120 miles or 350 miles and run out of gas.  No telling.  

[newdude]

15 hours ago, samuse said:

It’s not just the gauge. The gauge is always at 1/4 but it’s also not pumping from the rear tank sometimes so I might go 120 miles or 350 miles and run out of gas.  No telling.  

 

 

Sounds like your problem is the rear tank then or wiring to it that controls the rear pump.  You are getting intermittent rear pump issues.  Front pump sounds like its working fine but its not getting fuel from the rear all the time to keep the front tank full to run the truck.  

 

Could be bad wiring, bad rear pump, bad ECM, bad intermittent ground.  

 

 

DESCRIPTION AND OPERATION:

Fuel Transfer Pump (w/ dual fuel tanks)

 

The ECM provides ignition positive voltage to the coil side of the fuel transfer pump relay. The ECM energizes the fuel transfer pump relay, which applies power to the fuel transfer pump. When the primary (front) fuel tank level is less than 50  liters (13.2 gallons) and the secondary (rear) fuel tank level is greater than 5 liters (1.3 gallons), the fuel transfer pump is commanded on and continues to transfer fuel to the primary fuel tank until the primary fuel tank level reaches 70 liters (18.5 gallons) and then the fuel transfer pump is commanded Off. When the secondary fuel tank level drops below 5 liters (1.3 gallons) and the primary tank is below 50 liters (13.2 gallons), the ECM commands the fuel transfer pump on for 180 s to pump the remaining fuel to the primary fuel tank.

[HDCC18]

I have a 2018 CC with dual tanks. What is needed to remove rear tank permanently and still have a working fuel gauge?

[newdude]

13 hours ago, HDCC18 said:

I have a 2018 CC with dual tanks. What is needed to remove rear tank permanently and still have a working fuel gauge?

 

 

That's easy.  Just fix the rear tank so it works again. 

 

You won't be able to bypass it without tuning the ECM and that is gonna add up, especially if its a diesel.  And even once you pay the entry fees to get into the ECM, its a 50/50 shot if you can disable the stuff in there for the second tank.  

[redwngr]

 

A couple dual tank info articles -- 

 

Rear Fuel Tank and Fuel Transfer Conditions – TechLink 

 

Rear Fuel Tank and Fuel Transfer Conditions

January 16, 2020

Some 2015-2018 Silverado and Sierra models and 2019 Silverado 2500/3500 and Sierra 2500/3500 models equipped with the 6.6L Duramax diesel engine (RPOs LML, L5P) and dual fuel tanks (23.5 gallon/89 liter front tank and 40 gallon/151 liter rear tank) (RPO N2N) may have poor fuel transfer or the rear fuel tank may have collapsed. (Fig. 13)

 

Fig. 13

 

These conditions may be caused by dirt and debris collecting on the top of the rear tank and plugging the vent (Fig. 14, #1), resulting in the fuel tank being pulled into a vacuum and bending the fuel tank fuel pump module. (Fig. 14, #2)

 

Fig. 14

 

If these conditions are found, replace the fuel tank and fuel pump module. Refer to Fuel Tank Fuel Pump Module Replacement in the appropriate Service Information.

In addition, to help prevent the vent from becoming plugged again, install a piece of fuel hose to the vent (Fig. 15, #1) and route it down the fuel feed line. (Fig. 15, #3) Secure the hose with zip ties. (Fig. 15, #2)

 

Fig. 15

 

Refer to Bulletin #19-NA-277 for additional information and part numbers. 

 

 

 

Insufficient Dual Tank Fuel Transfer – TechLink 

 

Insufficient Dual Tank Fuel Transfer

June 26, 2024

Some 2024 Silverado 3500 HD and Sierra 3500 HD models equipped with the 6.6L Duramax Diesel engine (RPO L5P) may have a fuel gauge that drops to empty and an inoperative fuel transfer pump.

During diagnosis, the Engine Control Module (ECM) may show a fuel level percentage higher than empty. For example, it may show a 72.2% fuel level with 45.5 gallons remaining, but the IPC data may show a considerably lower number, such as 9%. The fuel level condition may be caused by insufficient fuel transfer with the dual fuel tank transfer system not transferring fuel properly from the rear tank to the front tank.

Fuel Transfer Inlet Port

The poor fuel transfer from the rear tank to the front tank may be due to a blockage in the fuel transfer inlet port at the A7 Front Fuel Tank Sender Assembly inside the fuel tank. (Fig. 8, #15) The assembly may have an internal check valve within the inlet port blocking the fuel from entering the front tank. If it is found that the A7 Front Fuel Tank Sender Assembly fuel transfer inlet port is blocked, it should be replaced.

Fig. 8

 

Before installing the new A7 Front Fuel Tank Sender Assembly, inspect it to make sure there isn’t any blockage. Use very low air pressure (below 5 PSI) to determine if the fuel inlet port is blocked or flowing freely.

Fuel Transfer System Diagnosis

When performing basic testing of the fuel transfer system:

• Verify that the fuel transfer pump (Fig. 9) will run electrically by using the scan tool to command the pump on. This test does not confirm that the transfer pump is pumping fuel.
• Use the scan tool to monitor the front tank and rear tank fuel level voltages. Proper fuel level sensor voltages for either tank level sensor are 0.7 volts = full tank and 2.5 volts = empty.
• To determine if fuel is being transferred from the rear tank to the front tank, monitor the fuel level sensor voltages while commanding on, or jumper power and ground to the fuel transfer pump. The fuel level should decrease (voltage increases) in the rear tank and the fuel level should increase (voltage decreases) in the front tank.

 

Fig. 9

 

For more details on fuel transfer pump diagnosis, refer to #PIT6159.