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Gas Gauge not working...Sometimes

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  #1  
Old 09-11-2017, 09:18 PM
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Join Date: May 2011
Location: Texas
Posts: 66
Gas Gauge not working...Sometimes

Hey Guys,
My gas gauge is occasionally not moving up at all. A couple of times I killed the truck and restarted it and it moved up just fine. Does anyone know of any wires or whatever to check out first?
Thanks!
Chuck
 
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  #2  
Old 09-12-2017, 06:57 PM
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Join Date: Jul 2004
Location: Easton, Pa.
Posts: 5,625
First how the level gauge works so you can get some idea what's going on.
The fuel pump has a variable resistor that changes value with level changes.
The dash 'processor' converts the voltage changes to digital
then drives the fuel level gauge.
Its not a simple old time gauge circuit.
Could be a ground, harness leads, the plugup at the tank, level unit or a dash malfunction function.
.
First thing I would do is run the Dash Hec diagnostics and step to the fuel gauge reading that will show as an Octal number representing the tank level.
If you know the tank level it should relate to the Octal number. If not assume to issue is between the dash and the tank.
When stepping to FUEL the following will be seen for some level if there is no issue.
Octal 255 = open circuit.
232= full stop.
215= full tank +/- 10.
178= 3/4 mark +/- 8.
138= 1/2 mark +/- 7.
93 = 1/4 mark +/- 5.
41 = E mark +/- 4.
54= Low fuel light.
0 to 18= shorted circuit.
None of the numbers are Decimal or Binary unless converted for no useful reason..
.
This why I recommend you start here.
To access this test hold the reset button in then Ignition to run.
The gauges should all sweep as the first test.
There after pulse the reset button to step through to the Fuel Octal number on the mileage readout and compare to the info above.
Sorry its not simple but a digital system in use.
Any other way is just looking and guessing.
Good luck.
 
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  #3  
Old 09-12-2017, 08:51 PM
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Thread Starter
Join Date: May 2011
Location: Texas
Posts: 66
Originally Posted by Bluegrass View Post
First how the level gauge works so you can get some idea what's going on.
The fuel pump has a variable resistor that changes value with level changes.
The dash 'processor' converts the voltage changes to digital
then drives the fuel level gauge.
Its not a simple old time gauge circuit.
Could be a ground, harness leads, the plugup at the tank, level unit or a dash malfunction function.
.
First thing I would do is run the Dash Hec diagnostics and step to the fuel gauge reading that will show as an Octal number representing the tank level.
If you know the tank level it should relate to the Octal number. If not assume to issue is between the dash and the tank.
When stepping to FUEL the following will be seen for some level if there is no issue.
Octal 255 = open circuit.
232= full stop.
215= full tank +/- 10.
178= 3/4 mark +/- 8.
138= 1/2 mark +/- 7.
93 = 1/4 mark +/- 5.
41 = E mark +/- 4.
54= Low fuel light.
0 to 18= shorted circuit.
None of the numbers are Decimal or Binary unless converted for no useful reason..
.
This why I recommend you start here.
To access this test hold the reset button in then Ignition to run.
The gauges should all sweep as the first test.
There after pulse the reset button to step through to the Fuel Octal number on the mileage readout and compare to the info above.
Sorry its not simple but a digital system in use.
Any other way is just looking and guessing.
Good luck.
While pulsing the reset button, will the milage readout actually say "Fuel Octal"?
 
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  #4  
Old 09-12-2017, 09:50 PM
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Join Date: Jul 2004
Location: Easton, Pa.
Posts: 5,625
No, only FUEL.
The number you see is an Octal number notation.
Sorry it confuses you.
A number is a number unless told to what base it was derived from. (Octal) in this case.
Good luck.
 
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  #5  
Old 09-12-2017, 10:30 PM
glc
glc is online now
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Join Date: Dec 2006
Location: Joplin MO
Posts: 35,027
What YEAR is your truck? The procedure only applies to 99-03.

Hold the reset button in and turn on the key. When it says test let it go. Then press the reset and repeat till it says FUELxxx where xxx is a number. I just did mine, I'm a bit under F on the gauge and my number was 206.
 
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