Auto Repair Q&A



Cooling System










Auto Repair Products

Fixing a Bad Fuel Gauge

Fuel level sending unit schematic

As a vehicle gets older, or in cases where bad gas or water has been added to the fuel tank, the fuel gauge may begin to act erratically or stop working altogether. Faulty or bad fuel gauges can be a headache and though there are ways around keeping track of fuel levels without a gauge, they can be inconvenient.

The first thing to do is determine if the sending unit, gauge in the cluster, or another problem is our issue. The first thing to do is to check all appropriate fuses and circuits. If the sending unit or its wiring are accessible without removing a lot of parts, test its circuit from there to the instrument cluster for the readout. There will be at least three interruptions: the fuse for the fuel system, the keyswitch, and the gauge itself. Each of these should be operating without problems. You should also pull engine error codes (even if there is no light) to be sure something isn't registering.

Often, the problem is a bad connector, especially the one mounted directly on top of the sending unit, outside of the fuel tank. If that is the problem, it's much easier and cheaper to replace than the sending unit itself (on models where they are separate pieces).

If the circuit and fuses are good, you likely have a bad sending unit. Testing the gauge is also going to be necessary, but on most vehicles, pulling the sending unit is likely easier and faster than is removing the fuel gauge in the dashboard.

Removing the sending unit is a relatively time-consuming job that requires some skill, but it is doable by most competent home mechanics. Most of the work involves gaining access to the unit, which is usually inside the fuel tank. On some vehicles, this is as simple as removing the bottom portion of the rear seat. On others, the tank will need to be "dropped" (mostly removed) from the vehicle. Be sure you're using proper safety equipment and working in a well-ventilated area as you will be exposing combustible fuel.

Once access is gained, removal of the unit is straight-forward. Replacing should also require putting in new O-rings and seals, which are usually part of the new sending unit kit (make sure before you proceed).

You should test the unit, which can be done with a circuit tester or Ohm meter. Refer to your repair manual for more information on your vehicle's specifics.