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Old 08-22-2016, 12:02 AM   #1
Red1968
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Fuel sending unit?

I bought a brand new 21 gallon fuel tank and matching sending unit for my 69 blazer from brothers truck parts and I have a new cluster from lmc. The issue I am having is I can fill the tank full of fuel and the gauge will read exactly full and it will go down just fine but when the fuel gauge is showing empty it will only hold about 14 gallons to fill it back up so something is not correct. Has anyone had this issue or does anyone know what could possibly be wrong?
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Old 08-22-2016, 05:26 AM   #2
orangek5
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Re: Fuel sending unit?

Maybe the gadge itself has a defect
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Old 08-22-2016, 09:01 AM   #3
jaros44sr
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Re: Fuel sending unit?

maybe they sold you a 14 gallon tank. what are the dimensions on your tank
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Old 08-22-2016, 09:36 AM   #4
Tom Vogel
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Re: Fuel sending unit?

You might want to post this question in the electrical forum as well.
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Old 08-22-2016, 10:43 AM   #5
Bigdav160
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Re: Fuel sending unit?

If you unplug the sensor does it go beyond full? If you short that wire to ground does it go below E? But if I had to guess, I'd say the resistance of the imported sending unit is not quite the same as the factory unit.
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Old 08-22-2016, 05:52 PM   #6
Red1968
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Re: Fuel sending unit?

My tank dimensions are 26x16x13 which comes out to be 22 gallons when you figure up the dimensions so it is a 21 gallon tank so something has to be wrong with the sending unit or the gauge itself. I was just trying to see if anyone else has had this same issue with there new sending unit or cluster before I tore into it deeper to try to figure out the problem.
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Old 08-23-2016, 09:41 AM   #7
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Re: Fuel sending unit?

To me, it sounds like the sender has the wrong resistance value for that particular gauge. I would check the actual resistances from the fuel sender when empty and full with an ohm meter, then check the part number of the gauge to see if it's compatible.
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