How can I fix or test my fuel gauge. It does not show anything and all my fuses are good.

Instruments are generally supplied with power from a common source and if the other dashboard lights and gauges work it is a fair assumption for the time being, loss of power to the circuit isn't the problem.

Most fuel gauge problems are caused by either the fuel tank ground being lost or the rheostat inside the tank sender failing.

In the traditional fuel gauge circuit when a bimetal, moving coil or moving iron gauge is used, the circuit can be tested simply by shorting the wire to the gauge unit to a good ground when the gauge would read full, proving the gauge and wiring is ok.

It is best to be aware other types of gauge might be used and modern digital vehicles might have to be treated differently - instead of being grounded a sensor substitute might be needed or simply test the tank unit with an ohm meter.

Here are the usual suspects:
stuck fuel valve/float valve in the carburetor.
clogged fuel filter. or fuel line.
defective fuel pump.
electric fuel pump may be just a blown fuse, or wiring problem. good hunting.

Cathy, 1996 Mercury cougar gas gauge not working. Simplest thing to check first is your fuel gage fuse, make sure all fuses are good. The ground wire could be corroded/damaged, sending unit in tank faulty, fuel level gauge in cluster faulty. All things can be tested by a good Tech.,diagnosed and estimate for repair.
1994 Mercury Cougar gas gauge don work
Ford Gas Gauge Does Not Work Help Blue Springs Ford Parts Blog
Diagnose Fuel Gauge

Courtney, Check the fuse first for the gage, if blown, replace. The gas tank will probably have to be taken out of vehicle to change the fuel sending unit. 1st Link shows how to test, other links will show replacement procedures.
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Fuel Gauge Troubleshooting

How To Install Replace Fuel Pump and Sending Unit Chevy Malibu 99 03...

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What year an make an model vehicle ?

I would bet the sending unit is bad but lets check it, a good test i use is that i have a used sending unit i connect to wiring to test the gauge and wiring, if the gauge moves when i move the testing unit then i know the gauge is good and the wiring to, locte the connector at fuel tank, and unplug it, this will be the one the leads to top of the tank and the connector will be on the side be the frame on drivers side, the way you know you have the right connector will be the truck will not run as this connector has the sending unit and pump wires in it, if the gauge goes to full then you know the wiring is good and the gauge is good, you can jump the two wires and gauge should go to full also. the problem is you must get the right wires for sending unit or you may pop fuse, let me see if i can get you a wiring diagram or just do the full test by unplugging connector.

Okay, your sending unit has a yellow and white wire, thats the sending unit wire, the other is a ground and we wont worry about that. so if you want to see if gauge will go to empty or full just unplug connector and gauge will move to full then if you take a wire and jump the yellow wire with white stripe to a good ground the gauge will go to empty, the thing is your gauge is on empty so sending unit may be grounded out, good day

have a Bora 1.9 TDI on 02 plate the fuel, temp not work, also airbag light is on all the time , we have check all the fuses on the side panel and the look ok, the lights and indicator are workign fine

Fuel gauge sending unit might of went out. My first guess, is the fuse. Look in your manual, see where fuel gauge fuse is and first replace it, if it just happend , it is mostly likely a fuse or connection issue.

hi this sounds like it could be a couple of things, first the obvious have you checked the fuse? or it might be the relay in the fuse box might need replacing, and the fuel sender unit in the fuel tank, you also can check out the wires going to the sender unit, sometimes you can find these under the rear seat or in the boot/trunk area might be a simple case of one of the wires have come adrift there is a couple of things to check before having the sender unit replaced or the Gage..hope that helps

It might not be anything wrong with your fuel sending unit. Keep an eye on your other gauges. I own a 2004 Pontiac Bonneville GXP. All of my gauges have started acting erratically. It started with my Temp. gauge, moved on to my speedometer, and now my oil pressure , fuel level and batty volt gauges are affected too. Its a very common problem with GM vehicles.