Hyundai Repair: fuel gauge, hyundai lantra, variable resistor

Question
QUESTION: Hi,
I bought an Hyundai lantra 1.6 gls last weekend , but the fuel gauge doesn't work at all. It sits on empty and stays on empty .. could you help me out please with what i have to fix in order to make it working again ?
thank you very much, Mark

PS. it is a uk model

ANSWER: Hi, Mark.  The fuel gauge is a rather simple circuit.  There are three wires going to the gauge-- a power, a ground, and a signal wire from the fuel sender, which is a variable resistor attached to a float.  When the signal wire is open, the gauge should read empty, and when it is shorted to ground, the gauge should read full.  

Since the problem is most frequently in the fuel sender, do the checking at the fuel sender first.  Simply unplug the sender and, with the ignition on, short the signal wire to the ground wire at the connector.  If the gauge goes to the full position, you know with 100% certainty the issue is in the sender since you just verified proper operation of everything else in the circuit.

If you follow up with the model year of your Elantra, I can probably give you the color codes of the signal and ground wires and their positions in the connector.

---------- FOLLOW-UP ----------

QUESTION: Hi again ,
it's a 1995 M reg lantra.
thx again ;)

Answer
I'm going to give you two scenarios here since Hyundai tends to introduce models elsewhere in the world prior to the U.S., so I'm not sure whether yours is comparable to our 1995 or 1996 models.  In either case, the sender should be accessible via a cover under the rear seat.

For the U.S. 1995 model:
The sender should be a three-pin connector with three wires.
Pin 1: Brown/blue for low fuel lamp
Pin 2: Green/gray for fuel gauge
Pin 3: Black for ground.
To check, simply unplug the sender and jumper the green/gray wire to the black wire.  The fuel gauge should (slowly) go to full.


For the U.S. 1996 model:
The sender and fuel pump share the same 6-pin connector.  You'll be interested in the following:
Pin 1: Black for ground
Pin 2: Yellow or Blue/yellow for low fuel lamp
Pin 6: Green/Brown for fuel gauge.
To check, unplug the connector and jumper the green/brown wire to the black wire.  The fuel gauge should (slowly) go to full.