Barry Barrett Posted on Feb 28, 2015

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2001 Buick Century, fuel gauge shows correct when I first start the car, and the "low fuel" light comes on at the correct time, but otherwise, always shows full. Can't be the sending unit, since it is correct every time I start the car (no matter what fuel level), and the needle is not the issue, for the same reason. What could be the issue?

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montehammons

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Posted on Feb 28, 2015

montehammons

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I'd still say the sending unit was malfunctioning. If you understand the sending unit has a variable resistor that the float arm rides across. From the dash gauge, a low voltage signal (usually about 5 volts) is sent to the sending unit in the tank, and then to ground. As the electric path crosses the variable resistor, that is what the needle measures- the resistance to ground, however much the float arm is set at. It sounds like your sending unit has worn sufficiently to not measure the resistance correctly, after the electric path is made. Hope that makes sense. Not likely the gauge or the signal to the sending unit is bad.

Randy Ohler

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Posted on Feb 28, 2015

Randy Ohler

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Only four tings it can be. The sending unit, the gauge, wiring or the PCM. So you are saying that you keep your car full all the time? Replace the sending unit. 99% of the time it is the sending unit. .9% of it could be a gauge. .1% is the PCM.

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Barry Barrett Feb 28, 2015

When I start the car, it always shows correct (1/4, 1/2, 3/8, etc) then moves to full after a few seconds. Every time I start the car. I think if it was the sending unit, be it the float or the resistor, it would never or rarely show the correct fuel level.
Randy Ohler Feb 28, 2015

How do you know it has that much fuel in it?
Barry Barrett Feb 28, 2015

mileage mileage

5 Related Answers

Ronny Bennett Sr.

6988 Answers
Posted on Jul 03, 2009

SOURCE: my fuel gauge reads full then suddenly drop to

replace the fuel sending unit

Anonymous

4669 Answers
Posted on May 18, 2009

SOURCE: Fuel gauge is stuck on full for a 2001 Buick

Gm cars are common for having defective fuel tank sending units in the tank. Yours likely needs replaced.

Anonymous

91 Answers
Posted on Apr 24, 2009

SOURCE: 2001 Buick Century fuel gauge

fuel sending unit is faulty needs replaced unfortunatly you will be forced to buy the entire fuel pump (module). they are not cheap.

Anonymous

468 Answers
Posted on Oct 20, 2009

SOURCE: 2000 Buick Century gas gauge reads full all the time

You're either looking at a short in the wire that goes to the fuel sender, or a bad fuel sender. If it was just a broken wire, it would read empty instead. The fuel sender is a permanent part of the fuel pump, so that has to be replaced as a unit.

Anonymous

600 Answers
Posted on Nov 01, 2009

SOURCE: 2000 buick century custom. fuel gauge fluctuates

The sender unit has a fine resistance wire with a slider to read the level, the slider or wires are worn and making intermittent contact, the low fuel light is a seperate switch so it will still work.access to the sender is usually under the rear seat cushon, under the soundproofing and a cover, have a look and describe what you have .

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