05 Trailblazer - Gas gauge after refueling not working

[BoxMN]

05 Trailblazer, 100k, in very good condition. I had the instrument cluster replaced a year or so ago, and not other issues there. I don't think this is a cluster issue, but not sure.

Gauge reads fine. But after one fill up, it went down to zero/empty (and the range matched the "empty" status). Then after some miles of driving, it came back up. Now, it works, but after refueling (every time) the fuel goes DOWN till the light comes on (right away after starting car again) and then it slowly but surely goes to normal, and works until the next refueling...

What could be going on? All other parts of instrument cluster are working, and we never ran it out of fuel, and nothing "runs" out of whack... funky... Thanks for any thoughts or advice.

[Jeremy airjer W]

Bad sending unit in the fuel tank.

[flyfisher03]

It could be that the fuel level sensor is sticky in the tank. This comes as a complete pump unit and is costly to replace. I would first recommend using a fuel system cleaner such as Chevron Techron might free it up.

[Jeremy airjer W]

The level sensor is or was serviceable. They ran about 125 dollars from the dealer. The pump assmebly will set you back about $500 from the dealer.

[flyfisher03]

In my opinion if you are already going to drop the tank to change out the level sensor you may as well do the entire pump assembly, because the pump may not be that far out from going out.

[Jeremy airjer W]

Surprisingly enough they are not that common on the trailblazer. In fact I may have replaced one that I vaguely remember.

[BoxMN]

Thanks guys. I think I will try the fuel cleaner first I am already using the Trip B odometer as a "just in case".

Second question, how hard is dropping the tank if I don't have a pit or lift? Worth even a novice trying it, or is it something to bring to shop? Thanks!