The fuel level gauge in my 99 Civic is stuck in the full position, most of the time.

Occasionally it would show the correct level briefly and then go back to full.

The gauge is all the way on empty when the car is turned off.

The low fuel light indicator does work.

1. What are some ways to test what is actually not working?

2. What can explain the fact that it sometimes shows the correct level?

Thank you.

 

Take out the back seat bottom cushion for access to the wires on the gas tank. Unplug the wires and turn the key on. The gauge should go to empty. If it doesn't, there's either a short in the wiring or the gauge head is bad. If it does read empty with the tank unit disconnected, the tank unit is probably bad.

 

There is no better answer than this^

 

Thank you. I'll try that simple test.

 

The gauge is now stuck in the full position whether the car is running or not.

I unplugged what I think is the sending unit. See photo below. Did I unplug the correct thing?

With this unplugged, I turned the ignition to "on." The gauge still shows full.

What's the next step?

Thank you.

 

With the sending unit and gauge cluster unplugged, use a multimeter to check for a short in the wire that runs between the gauge cluster and the sending unit connectors.

 

I have a multimeter but don't really know how to use it...

1. How do I know which cluster wires / pins to test?

2. I am not sure my multimeter wires are long enough to get from the sending unit to the cluster wire. How do I address that?

3. Any advice on how to use a multimeter to test the short would be appreciated.

Sorry for the novice questions.

 

And what does it mean that the needle is stuck in the full position even when the car is turned off?

 

probably the sender unit flote is stuck you could try adding some seafoam to the gas in hopes of cleaning the unit but most likely it needs to be replaced.or it could be a dash malfunction.

 

The sending unit has the 3P connector whereas the fuel pump has the 2P connector.