Fuel gauge not working

2008 KIA RIO
155,000 MILES
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LOU20
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I filled my gas tank but my needle showing Empty. This problem started over the weekend. It started working properly again. now it's back not working. Still going back and forth from F to E.
Jun 3, 2022 at 1:18 AM
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SQM
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Hello,

This issue could be due to a faulty fuel level sending unit. The fuel level sending unit consists of a resistor panel and a float. As the float moves up/down it registers a different value on the resistor panel, that gets sent to the gauge.
Over time the resistor can go bad and send incorrect signal to the gauge.

The level sender is part of the fuel pump.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

I have attached diagrams below for your reference.

Let me know of any questions.
Thank you.

Jun 3, 2022 at 10:45 AM
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LOU20
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So, I will need a fuel pump?
Jun 3, 2022 at 6:37 PM
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SQM
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That is likely the issue, yes.
Jun 3, 2022 at 7:33 PM
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LOU20
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Hello, following back up I change the fuel pump and my fuel gauge is still going from full to empty. What else could possibly be causing it not to read correctly?
Oct 28, 2022 at 7:09 AM
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SQM
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Was there any corrosion of the fuel pump connector?
If the signal wire for the level is corroded or loose it won't send the signal to the gauge.
Oct 30, 2022 at 10:00 AM
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LOU20
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I will have to ask the mechanic who changed the fuel pump. When it read E and I turn the car off and then back on it reads correct.
Nov 11, 2022 at 8:19 PM
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SQM
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The signal wire might have too much resistance due to corrosion or heating up. That could be why it reads correct when you shut off and turn back on.
Nov 11, 2022 at 9:48 PM
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LOU20
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Where are the signal wires located?
Nov 17, 2022 at 3:47 PM
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SQM
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That is the connector that is attached tot he fuel pump module. See attached diagrams. That plug could be corroded or have bad connection.
Nov 19, 2022 at 6:55 AM