Fuel gauge shows when tank is a quarter down it reads on bottom of guage, opposite of where it should be. 2007 Honda civic

most fuel gauge readings are not that accurate anyway so its out of fuel but not what the is guage reading. but the fuel level sensor in the tank may be at fault sound like its the prob but the instument pack should put the low fuel light on if its fitted on your vehicle spec but not always fitted even though the warning light is present hope this helps

Fuel pumps outside the gas tank have nothing to do with fuel gauge readings. There is a fuel level sender unit inside the tank with a float which supplys variable ground circuit to the gauge. If you can find the wire to this unit, you can ground it to see if the gauge now goes to full. If so, sender unit in tank is bad, or has bad wiring/ground.

The gas tank sounds like a bad ground usually located under the car at the gas tank. I do not know but maybe they both tach and fuel gague get their ground from the same place.

I'm not sure I am understanding your question. The low Fuel indicator light comes on, depending on how sensitive it is set, when you have between 2 and 5 gallons of gas left in the tank. This also depends on how accurate your fuel level sending unit is reading the fuel level in the tank. The low fuel level light depends on the level of fuel in the tank itself but other than using that sensor it has nothing to do with the fuel gauge itself. The fuel gauge may or may not be accurately showing the fuel level.

Open circuit - gauge will read full.Grounded circuit - the gauge will read empty. If it reads empty all the time - then the wire that goes to the sender is broken and/or grounded somewhere along its length to the fuel tank. run a jumper wire from bottom of the fuse box in the spot, all the way to top of sending unit on tank. disconnect old wire at both ends, and then turn on the key and observe guage. if not this, check guage itself for sticking.

When testing a fuel guage you should disconnect the wires to it,guage should read over full,ground the float wire,turn off key then turn back on should read empty.You have to cycle the key for guage to move.If still inop the wire is broken in the harness between the tank and the dash.Voltage on the float wire is low.When tested with a test light it will barely light the light and pulsate.This test indicates the wiring is good.

THIS PROBLEM IS ONLY CAUSED BY ONE THING, AND THAT IS A DEFECTIVE GAS GAUGE SENDING UNIT IN THE GAS TANK

there is little else that causes this except the fuel guage sending unit in the gas tank.

The most likely culprit is the sending unit in the tank. They are relatively easy to change, as long as you don't have much fuel in the tank. It's a mechanical unit that has a float that raises and lowers with the fuel level, however with age, the floats can develop leaks and no longer float, of the electronic portion of the unit can go bad and not register the proper level. They are replaced and an entire unit, so it doesn't matter which happened, you will need to change the fuel tank sending unit.

The problem is the fuel guage sending unit, this is in the fuel tank, it will have to be changed out.