Erratic Fuel Indicator

I have a 2000 Chevy Blazer that recently developed a condition where the fuel gauge is erratic. When the tank is full the gauge registers properly. However, as soon as it moves off full (after driving around 25 miles), the indicator begins to fluctuate, moving between 1/2 and the correct reading. While not a critical condition, it is annoying and something I would like to have corrected if it is not an expensive fix. Specifically, would there be a simple fix, and is this something I could do myself? Thanks for any assistance you can provide.

Lauren Cady


It may be a loose baffle. Some tanks have wells welded to the bottom of the tank as a baffle. This keeps the fuel gauge from jumping by stabilizing the fuel at the sender. Some GM trucks have long narrow tanks mounted longitudally and require the stabilizing wells. If that is the problem replacing the tank will be the solution.

I had this problem on my 2006 Chevrolet Uplander. The sending unit in the fuel tank was defective. Apparently, this is a GM problem. The service writer at the dealership knew right away what the problem was. My Uplander was under warranty and was fixed with no questions asked nor any cost to me.

The electrical contacts on the sender inside the tank may be dirty. Some folks have used a product made by Chevron called Techron to help clean the contacts and fix this kind of trouble with success. You just pour the bottle into the tank before a fill up. If one application doesn’t work try a second one. If that still dosen’t work then you will most likely need to replace the sender unit.

My deepest condolences, I also have a 2000 Blazer. The fuel gauge on my Blazer hasn’t worked in over 2 years. Evidently sulfur in the gas contaminates the sending unit. The sending unit is part of the fuel pump assembly, so the fuel pump has to be replaced ($$$) to fix it. It seems to be common on GMs of this vintage.

I keep track of my mileage and refill with at least 3 to 4 gallons left in the tank, i.e. 240-255 miles in the winter and 255-270 miles in the summer.

Try 1 or 2 treatments with Chevron Techron, it’s supposed to clean the sending unit. Even if it doesn’t help, the truck will run smoother.

Ed B.