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I've got a 01 3500 Dmax that has dual tanks. The truck is not transfering the fuel from the rear tank up to the front. It has the electronic pump thats mounted between the tanks that is suppposed to regulate the level of fuel between the two tanks. I replaced the pump and checked the relay under the hood and its still not working. The truck is running off of the front tank only. Which by the way, really sucks because its a sweeper truck with a second 4 cylinder diesel pony motor.

The gas gauge has always been messed up in that it randomly drops to E and says low fuel, even when its not low. Now its just pegged on E with "Low Fuel" on the dash. Two engines running off of one tank with no fuel gauge kinda stinks. Its just a matter of time before I run this thing out of fuel.

Is there some kind of control module or something that controls when the pump turns on? Any advice or help would be great because this is quite annoying.
 

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You could put a switch in to manually turn on the pump. I bet since the fuel gauge is messed up, that has something to do with the transferring. I'm not sure how that system works, but normally you would have a float or something of the sort to tell the pump to transfer the fuel.
 

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I am having the same problem. Did you get any answers to this problem. I replaced my front sending unit and transfer pump, but had no luck. My rear tank is full, but can not get front tank to fill. I checked for 12 volts at the pump motor and have none. Anybody have any suggestions????
 

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If the transfer pump is signalled to transfer via the faulty sending unit (gauge being wrong), you won't ever get the pump to work properly as it needs the OEM sending unit to turn the pump on/off automatically.

You could try "hotwiring" the transfer pump and running it from a switched source current, but it then defeats the automatic fuel transfer feature.

Nutshell - get the sending unit fixed. JMO, FWIW...

Regards,
Keith
 

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I am having the same problem. Did you get any answers to this problem. I replaced my front sending unit and transfer pump, but had no luck. My rear tank is full, but can not get front tank to fill. I checked for 12 volts at the pump motor and have none. Anybody have any suggestions????
It's a possibility the SU wiring may be reversed, making the rear SU govern the TP instead of the OEM SU governing.

Just a thought.

Regards,
Keith
 

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GM has a bulletin out for that issue. Generally the cause is in the rear tank, when going over bumps the float arm jumps up past the stopper on the sender and in some cases stays there. This causes an open condition, when this happens the fuel guage will read empty and vehicle will not transfer and fuel from the rear tank even though is has fuel in it.
 

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I've got a 01 3500 Dmax that has dual tanks. The truck is not transfering the fuel from the rear tank up to the front. It has the electronic pump thats mounted between the tanks that is suppposed to regulate the level of fuel between the two tanks. I replaced the pump and checked the relay under the hood and its still not working. The truck is running off of the front tank only. Which by the way, really sucks because its a sweeper truck with a second 4 cylinder diesel pony motor.

The gas gauge has always been messed up in that it randomly drops to E and says low fuel, even when its not low. Now its just pegged on E with "Low Fuel" on the dash. Two engines running off of one tank with no fuel gauge kinda stinks. Its just a matter of time before I run this thing out of fuel.

Is there some kind of control module or something that controls when the pump turns on? Any advice or help would be great because this is quite annoying.
It endes up that I have a similar fault with one of the company trucks. A 05 3500 WITH A 6.6 I HAVE DISCOVERED THAT WHEN THERE IS A PERFORMANCE ISSUE WITH THE SENDER/S ON THIS TRUCK IT SET A CODE THAT HAD TO BE CLEARED IN ORDER FOR THE TRANSFER PUMP AND GAUGE TO COME BACK ON LINE. WE WERE ABLE TO EXTRACT BOTH DENDERS A TEST THEM TO FIND THE FRONT ONE WITH GLITCHES HAPPENING THRU THE TRAVEL RANGE....WITH THE FRONT SENDER UNPLUGGED I CLEARED THE CODE AND INSTANTLY THE GAUGE WORKED AND THE PUMP STARTED RUNNING TO PULL FUEL FROM THE REAR TANK.. O HAPPY DAY.
 

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It endes up that I have a similar fault with one of the company trucks. A 05 3500 WITH A 6.6 I HAVE DISCOVERED THAT WHEN THERE IS A PERFORMANCE ISSUE WITH THE SENDER/S ON THIS TRUCK IT SET A CODE THAT HAD TO BE CLEARED IN ORDER FOR THE TRANSFER PUMP AND GAUGE TO COME BACK ON LINE. WE WERE ABLE TO EXTRACT BOTH DENDERS A TEST THEM TO FIND THE FRONT ONE WITH GLITCHES HAPPENING THRU THE TRAVEL RANGE....WITH THE FRONT SENDER UNPLUGGED I CLEARED THE CODE AND INSTANTLY THE GAUGE WORKED AND THE PUMP STARTED RUNNING TO PULL FUEL FROM THE REAR TANK.. O HAPPY DAY.

I know this thread is really old but i saw your response and wanted to second it. We've got a lb7 4500 at work that has had issues from day one with the fuel tanks and gauge and that's what it always, some random code i can never find any good info on and if i clear it all works good for 6 months to over a year.
 

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Hello, We have a 2014 3500 duramax that is not transferring diesel from back to front. The gauge reads 1/2 full, but twice it ran out of fuel. The truck just shuts off no brakes nor steering. Kinda dangerous. We replaced the sending unit. Still not transferring.
 
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