gas gauge wacky?

[darrylb]

Has anyone experienced this? When my 2000 Lesabre gets to about 1/4 of a tank or lower on fuel the gauge will show up to half a tank and the lower the tank gets the more the gauge goes to full. I wish this was really happening and I would never get rid of the car. Any ideas? The sender in the tank? The gauge?

Thanks!!

[wrightz28]

You shouldn't be letting your tank get that low.

[Smith1000]

The sender is in the tank. I have a 97 Lesabre and had problems with the fuel gauge. Ended up putting in a salvaged sending unit, but I would first check the sending unit ground wire to make sure it is getting a good ground. That might fix the problem.

The sending unit itself is a kind of a varible resistor that sends out different ohm readings depending on the level of the tank. It works off of a float arm in the tank. From what I recall, 0 to 240 ohms is the range. If the resistor is failing at lower tank level and reading higher, it may be because the resistor is sending false (too high) readings. If so, you will likely need a new sending unit. I substituted resistors from Radio Shack with known values to determine if the problem was the sending unit. For example, resistors that added up to 120=1/2 tank. This confirmed the problem was the sending unit rather than wiring, gauge or ECU signal.

In the 97, the slavaged piece included a fuel pump and sending unit all together. Not sure, but I think they can be separated if needed. Either way, I believe the part/s new are fairly expensive. That's why I put in a salvaged one.

The signal goes into the ECM for "buffering" before reaching the gauge in the dash. This helps prevent a "sloshy" gauge and accounts for the shape of the tank as well.

I would check the ground wire first and make sure the wiring looks okay. I remember reading that a certain type of gasoline was corrosive to the sending unit. The one I replaced was just worn out and for whatever reason, it was sending wrong ohm values. Good luck with it.

[BNaylor]

Originally Posted by Smith1000

The sending unit itself is a kind of a varible resistor that sends out different ohm readings depending on the level of the tank. It works off of a float arm in the tank. From what I recall, 0 to 240 ohms is the range. If the resistor is failing at lower tank level and reading higher, it may be because the resistor is sending false (too high) readings. If so, you will likely need a new sending unit. I substituted resistors from Radio Shack with known values to determine if the problem was the sending unit. For example, resistors that added up to 120=1/2 tank. This confirmed the problem was the sending unit rather than wiring, gauge or ECU signal.

In the 97, the slavaged piece included a fuel pump and sending unit all together. Not sure, but I think they can be separated if needed. Either way, I believe the part/s new are fairly expensive. That's why I put in a salvaged one.

Your assumption is correct. Plus it is cheaper. $85 for the AC Delco float level kit new. See pics below.

[Smith1000]

Nice pics. Looks like there is access through the trunk on the vehicle in the pic. I had to drop the tank to replace the sending unit on the 97 Lesabre. I read that the sending unit could be accessed through the trunk in the Park Avenues though.

[BNaylor]

Originally Posted by Smith1000

Nice pics. Looks like there is access through the trunk on the vehicle in the pic. I had to drop the tank to replace the sending unit on the 97 Lesabre. I read that the sending unit could be accessed through the trunk in the Park Avenues though.

Thanks. I believe they added the easy access for 2000 and up LeSabre without having to drop the gas tank. Not sure of the years for PA. Also, '97 and up Regal and Century have the easy access. Makes the job a lot easier.

[darrylb]

Thanks for all the advice. This forum is great and so are the participants!!