Dual gas tanks

[Hossman5561]

Rear tank abandoned, why wont gauge read for front and how can it be fixed?

 

[Will L.]

You need to put out a lot more info for any chance of Help. Make, model, year, if fleet truck, rv, etc.

Depending if truck is newer and they feed through a bcm to the gauge you may not be able to ever have it read properly. Might have to do secondary fuel gauge feed from a secondary float sensor you rig up.

 

[Hossman5561]

Sorry for lack of info; truck is a fleet vehicle and is a 2001 chevy 3500 not sure of engine size. Has a flat dump bed and some one stuffed a 2or through top of rear tank, was quoted 1400+ to replace tank due to being a special tank

 

[Hossman5561]

Right now gauge reads empty all the time with low fuel light.

 

[THEFERMANATOR]

That setup runs each sender to the PCM, it then controls the fuel gauge to show the combined capacity if both tanks on 1 gauge, and controls the transfer pump to move fuel from the rear tank to the front tank as needed. The high pressure pump for the engine is mounted in the front tank and is the only tank it runs the engine from, hence why it has to move the fuel from the rear tank to the front tank. Anytime it sees a problem with either sender or fuel not transferring as commanded, it puts the fuel gauge to empty.

Your fixes are either replace the rear tank and fix the sender, install a 40 ohm resistor across the rear sender wires so it thinks the rear tank is always empty and it will only use roughly half the fuel gauge, or have your PCM flashed to a tune from a single tank truck so that it will only read the front tank.

 

[Hossman5561]

That setup runs each sender to the PCM, it then controls the fuel gauge to show the combined capacity if both tanks on 1 gauge, and controls the transfer pump to move fuel from the rear tank to the front tank as needed. The high pressure pump for the engine is mounted in the front tank and is the only tank it runs the engine from, hence why it has to move the fuel from the rear tank to the front tank. Anytime it sees a problem with either sender or fuel not transferring as commanded, it puts the fuel gauge to empty.

Your fixes are either replace the rear tank and fix the sender, install a 40 ohm resistor across the rear sender wires so it thinks the rear tank is always empty and it will only use roughly half the fuel gauge, or have your PCM flashed to a tune from a single tank truck so that it will only read the front tank.

Just a thought; is it possible to wire both sending units from front tank to fool computer for gauge opperation?

 

[Will L.]

Thats the part he said about adding a resistor inline of the rear tank.

 

[THEFERMANATOR]

Just a thought; is it possible to wire both sending units from front tank to fool computer for gauge opperation?

Negative, if the fuel levels do not follow what it expects from them, it will revert the gauge to empty. All you can do is to install a resistor so it thinks the rear tank is always empty, then it will show roughly a half tank when the front tank is full.

Just dawned on me you said it's an 01, which body style 01 is this? Does it look like a 88-98 style truck or a 99-06 style truck? Is it a 3500HD or just a 3500? If you have the 99-06 3500 body style truck all the info I gave is correct, if it is the 88-98 3500HD body style none of the info I gave is correct.

 

[Hossman5561]

Negative, if the fuel levels do follow what it expects from them, it will revert the gauge to empty. All you can do is to install a resistor so it thinks the rear tank is always empty, then it will show roughly a half tank when the front tank is full.

Just dawned on me you said it's an 01, which body style 01 is this? Does it look like a 88-98 style truck or a 99-06 style truck? Is it a 3500HD or just a 3500? If you have the 99-06 3500 body style truck all the info I gave is correct, if it is the 88-98 3500HD body style none of the info I gave is correct.

It is a regular 3500 as far as I can tell, at least it is not badged as a HD;

 

[THEFERMANATOR]

Ok, all the info I gave you is correct for that truck.