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Guest nikirushka
Posted

I've had my 2001 forte for just over a year now, and the fuel guage has been wrong from the start.

 

It reads 1/4 of a tank plus a little bit (bout 1.5mm) above where the fuel actually is - so, when the guage tells me I have 3/4 of a tank, I actually have just under half a tank of fuel.

 

The light still comes on at the right time though.

 

The fuel sender unit was replaced with a brand new one a couple of weeks back and it made no difference at all.

 

All other clocks/guages are working fine, fuses fine to the best of my knowledge. The mechanic thought it was possibly an electrical fault somewhere.

 

Any ideas on what this might be?

Posted
Fuel gauges are never very accurate. From full, my last Xantia did 100 miles before moving off the full mark. It took ages to get to half-full. Then quickly dropped towards empty.
Posted

Important question - Does the gauge read full when you fill the tank? If so, the inaccuracy is exactly as John Douglas explained. MY BX was the same, and my 406 (very close to being the same car minus hydraulics) is not far off.

 

If not:

 

The fuel gauge is usually a resistor that is short when full and maximum resistance when empty.

 

If this is the case then shorting the wire going to the sensor to ground should make the fuel gauge read full.

 

If it does not, then the gauge on the dashboard is faulty, or there is a high resistance path in the wiring.

 

If shorting the wire to ground makes the gauge read full, then the gauge is fine.

 

Worth getting a wiring diagram if you want to fix this problem, as it's not worth risking shorting wires to ground without knowing exactly what's on them. You could also measure the voltage to the sender - this is sometimes from a voltage regulator which may have gone wrong, sending the wrong voltage so you getting the wrong reading.

Guest nikirushka
Posted

I'll get someone else to fix it, just need an idea of what it might be.

 

If I fill the tank right up the fuel guage just sits a quarter and a bit of a tank about the full line, so it's sitting in the void beyond the full mark.

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