How to Test the Fuel Gauge to See If It Is Workingby Chris Hoke
There are two main components to the fuel gauge system: the sender unit that measures the amount of fuel in the tank, and the gauge itself that displays the amount of fuel to the driver. When the gauge, the sender unit, or the required wiring between them do not function correctly, the fuel gauge may read falsely or simply not function at all. There are some simple tests you can do to see if your fuel gauge is working.
Ensure that all wiring connections (both on the back of the gauge and on the sender unit) are clean, tight, and free from dirt and corrosion. Checking the wiring on the back of the fuel gauge may require going underneath the dashboard, removing the instrument panel, or removing the gauge from the dashboard. The sender unit is located on the fuel tank and, in many vehicles, it is accessible under the back seat or trunk. This may require removing and lifting out the back seat or trunk carpet. Consult your service manual if you are unsure as to how to access the back of the gauge or the sender unit.
Turn the ignition on and off several times in succession and note if the needle moves at all. If there is no movement, check the fuse. The fuse panel may be located under the hood or under the dashboard. Each fuse should be labeled with an amperage rating and a number or series of letters indicating which circuit the fuse protects. Reference your service manual to determine where your fuse panel is located and which fuse controls the fuel gauge system. Replace the fuse if it is bad, making sure that the replacement fuse is the correct amperage rating.
Connect the jumper wire to the ignition switch and the terminal on the back of the fuel gauge, then turn the vehicle on. If the gauge now works, replace the defective wiring between the gauge and the ignition switch.
Ground the gauge by soldering or clipping one end of the jumper wire onto the gauge's grounding terminal and the other end onto a clean contact point on the vehicle's frame, then turn the vehicle on. If the gauge starts working, replace the defective fuel gauge grounding wire.
Ground the sender unit with the jumper wire using the method described in the previous step. The sender unit can be grounded by attaching the jumper wire to the exterior of the fuel tank or the vehicle's frame. Replace the sender unit's grounding wire if the gauge begins to function.
Disconnect the wire that connects the fuel gauge to the sender unit, then turn the vehicle on. If the fuel gauge reads full, this indicates a problem with the sender unit or the in-tank mechanism. If the gauge continues to read empty, you most likely have a faulty fuel gauge that needs to be replaced.
- After replacing the fuel gauge, if there is still a problem with the fuel reading, consult a mechanic.
- Ensure there is fuel in the tank before beginning these steps.
Things You'll Need
- Fuel gauge
- Service manual
- Jumper wire
- Disconnect your car's battery before handling potentially live wires.
Chris Hoke is a freelance writer, blogger and musician living in the San Francisco bay area. He began writing professionally in 2005 and his articles regularly appear on EmailServiceGuide.com and Slapstart.com.