2001 HYUNDAI FUEL GAUGE

Sounds like the float sender unit in the petrol tank is stuck

power goes through the gauge down to the sender unit ,through the resistance to ground
what you have indicates a short in the wire after the gauge and before the sender unit

gead short in the wire from the gauge to the sender unit
the gauge works by the variable resistance in the tank unit so when the gauge is full there is low resistance so the gauge reads full
reading full all the time indicates that there is power flowing through the gauge to a ground before the sender unit in the tank

There might be but it is unlikely a fuel gauge is fused alone; usually if it is a fuse other things will stop working too but I suggest you are guided in this matter by your car handbook.

Problem is probably wiring and in particular the grounding of the fuel tank sender unit. It could be a faulty sender but they are usually quite reliable.

Test by disconnecting the wire from the sender unit at the fuel tank and short to a good ground and the gauge should read full. If the gauge wire is in a block with other wires it will be necessary to positively identify the gauge wire before testing.
If the gauge reads refit the wire and duplicate the ground wire to a known good ground. If the gauge still reads the fault is a bad ground to the tank sender unit and if it doesn't the sender unit itself is probably faulty.

If grounding the gauge wire does not produce a reading the fault is the wiring to the tank, the supply to the gauge or a problem with the gauge itself.

I think the sending unit was damaged on installation or is defective. Did you use a factory OEM part.

Change the fuel gage sender unit in tank.its faulty.

The sending unit in your tank is going bad replace it.

This is a normal concern.
The instrument cluster uses 4 different operating modes to calculate the fuel level:
Anti-slosh (default mode)
Key OFF fueling
Key ON fueling
Recovery
After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.
The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).
The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The key must be in the OFF position throughout the entire refueling of the vehicle.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 15 ohms ± 2 ohms and 160 ohms ± 4 ohms.
If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.
The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The transmission is in PARK (P).
The key is in the RUN position.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
In key ON fueling mode, a 30-second timer activates after the transmission is put into the PARK (P) position (automatic transmissions). When the 30-second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), the fuel gauge strategy reverts to the anti-slosh mode. The key on refueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.
Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input during a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:
The instrument cluster is in the anti-slosh (default) mode.
The actual fuel level in the tank is greater than what is being displayed by the fuel gauge

Sounds to be a faulty tank sender unit, these senders use a fine coiled wire on which a brush slides along to vary its resistance.
If the coiled wire breaks midway, the only readings will be full or empty.
I think sender unit is mounted to internal fuel pump on this model (top of fuel tank)
Hope this helps, regards

this is an old post so not sure if problem has been resolved ?? but if not ? from your symptoms it sounds like the fuel tank sender unit is faulty and unfortunately not servicable but not too expensive to diy a new unit for a quick confirmation it is sender ? remove the wire from sender unit then scratch /hold to good earth whilst ignition is turned on and fuel guage is read by assistant ? if guage goes to full ? sender is faulty hope this helps?