How to wire the fuel gauge - Cars & Trucks

Check the wires going to the instrument cluster, and check the wires from the sending unit. Possibly a corroded or damaged wire/connector

That won't affect the fuel gauge. Different circuits, entirely. Any issue with the fuel gauge is between the gauge on the dash, a little wiring to the gas tank, and the sender unit inside the tank. In most cases, the problem turns out to be the sending unit inside the tank.

To check the gauge itself for working, you can ground the fuel gauge wire at the gas tank connector, and watch for movement on the gauge, with the key in ON. You take the connector off at the gas tank, find the wire for the fuel level sender (or gauge), and touch it to a good ground- a metal piece on the car frame. If gauge is good, the needle will move either to full or to empty, but you can see the needle move to a new point, when you (temporarily, only temporarily) ground the fuel gauge wire. The key in the switch must be in on. If this causes the needle to move, then the dash gauge is good, and the problem is the sender unit in the tank. This unit has a variable resistor, not too expensive. The fun is getting to it.

The power wire from the sending unit runs to the gauge. Since it is showing 3/4 all the time. It is a break in the wire or really high resistance. I would check resistance of the ground wire first. If it is good(less than 5.0 ohms), I would replace the power wire from the pump to the gauge. I assume the gauge goes to empty with the key off. If not the gauge is bad.

The fuel gauge is directly controlled by the fuel sending unit inside the fuel tank, it sends a ground return signal back to the fuel gauge. I am assuming of course that your fuel gauge is okay. To test your fuel gauge, connect the wire which goes to the fuel sending unit to chassis ground. Your fuel gauge should respond and indicate Full Tank. If not, there is a broken wire somewhere between your fuel gauge and the sending unit. Before connecting the wire that goes to the sending unit to ground, check it first with a DC Voltmeter, you should be able to read +12volts. Be sure that you turn your ignition switch to it's ON position.

check voltage to pink wire should be 5 volts ,it is power to senser would help to know type of car.

Of readings are inconsistent with known fuel levels, Ground (or connect to a tester light) the sender unit wire and watch if the gauge rises.

The repair manual for your year,make and model, will have the wiring diagram you'll need to re-wire the fuel gauge.

there is two things : fuel gauge and dash fuel gauge. The fuel gauge in tank rated to 0 to 90ohms.disconnect wire at the tank take a variable resistor connect it to wire .read the dash gauge if it move as you move the resistor. if ok fuel tank gauge is at fault

Ensure that all of the wire connections are clean, secure and corrosion-free.

2 Check your fuel gauge fuse if the gauge's indicator stays on empty when your turn on the ignition. If the fuse is good, join the sending unit connector to ground. Replace the sending unit if the gauge indictor moves to the full line.

3 Ground the terminal located on the back of the fuel gauge with a jumper wire if the indicator doesn't move. If it does move, consider replacing the wire between the fuel gauge and the sending unit. A poor ground is frequently responsible for fuel gauge problems.

4 Release the wire that connects to the fuel tank's sending unit. Confirm that there's no worn insulation that would permit wire contact to the body or frame. A fuel gauge reading of full generally indicates a problem with the tank unit, not the wiring.

What was the original problem? Most fuel gauge problems are either a bad fuel tank sending unit or a bad ground wire going between the sending unit and the frame of the car. The gauge and wiring can be easily tested using only a 12 volt test lamp, once you have access to the wiring at the fuel sending unit. This often requires draining the fuel tank and lowering it from the vehicle.
To test the gauge in the dash and it's related wiring, connect the 12 volt test light between the wire between the gauge and the sending unit (the one with power in it with the ignition on). Make the connection near the fuel tank sending unit. Connect the alligator clip on the test lamp to a known GOOD ground. The bulb in the lamp should glow dimly. The dash gauge should read somewhere between 1/4 to 3/4 of a tank of gas. (Varies with make and model) This will verify that the gauge is either good or bad.