2009 Buick LaCrosse - Fuel Level started reading funny. Any ideas?

[3800Series]

It may well be from sitting so long, this issue was also very common with GM Saab cars. Saab had a TSB that said to first try 20oz of Techron in an low tank then fill it before going into any actual repairs.
I have seen this work well on other vehicles like Chevy Venture, Grand Prix, Buicks, a VW Golf and a few others, some it doesnt help at all. Definitely worth trying before getting any deeper into it.

Agreed, very common for these vehicles and fuel system cleaners have always been my recommendation for it. Not a guaranteed fix but more often than not it does help. I've always recommended half a can of Berryman B-12 on a near empty tank, drive it down the highway until the gas light comes on. Put the other half can in, fill it up and on the next tank Gumout with PEA/Techron.

At the very least if it should make a noticeable difference.

 

[R18Civic]

Agreed, very common for these vehicles and fuel system cleaners have always been my recommendation for it. Not a guaranteed fix but more often than not it does help. I've always recommended half a can of Berryman B-12 on a near empty tank, drive it down the highway until the gas light comes on. Put the other half can in, fill it up and on the next tank Gumout with PEA/Techron.

At the very least if it should make a noticeable difference.

I almost went the berryman route but I read some things about people ending up with engine troubles after using it so I decided on Chevron Techron. Two treatments is the same price as redline fuel system treatment.

 

[measureman]

I was recently given a 2002 Blazer and was warned to fill it when the needle shows a 1/2 tank because past that the needle will bounce up and down.
I put a bottle of Techron in then followed with a bottle of MMO.
Now it does not fluctuate.
So not trusting it I fill it when it hits 1/2 and it takes 9 or so gallons for an 18 gallon tank, pretty accurate.
The last fill up I let it go almost to 1/4 to see and it again took 9 gallons.
Not going to trust it.
I now reset the trip odometer and when it shows 140 miles I fill it.
The blazer gets 14 MPG so 140 miles takes 10 or so gallons.

 

[GMBoy]

Run a double dose of TECHRON. GM TSB's actually instructs you to do this as a 1st step. The contacts on the sender unit gets sulpher build up from low tier gas. Only Techron has proven to be able to fix this issue. If it doesn't then there is a problem with the unit and you have to replace it. I know FCA had issues with RAM fuel pumps and they had to be replaced because the contacts were cheaply made and wore off early....I had to replace the fuel pump in my RAM for this issue.

Try Techron 1st...

 

[cartech]

I have a 1998 Dodge Caravan 2.4 L that has 172k miles. At about 167K (Aug 2022) I had the fuel filter replaced. The next morning there was gas under the vehicle, on the cement driveway. When I went back to the mechanic, he checked it out and found a fuel pump plastic fuel terminal cracked. Well since the previous mechanic was not wearing a BODY CAMERA...there was no proof that it happened when the fuel filter was replaced. DUH.. So I paid for the new fuel pump and install labor was free. They put in a Bosch fuel pump. That fuel pump reads 1/4 tank low. Anyway 2 years AND 2 months later (2 months after warranty expired) , the fuel level was at E when I started the van. It then started to fluctuate and PING, PING. I went back to mechanic and the quote to replace was $540. I visited sites to see what was going on and read about the resistor sensor and fuel additives. I bought 2 smaller bottles of Techron PLUS and put in gas tank.. Seemed to make a difference reducing the fluctuating. 2 days ago it started pinging like crazy and this morning the level was at E with 2/3 tank. and then pinged again and fluctuated. I drove to a NAPA store to ask what was the best KICK butt fuel cleaner. He said Lucas and Liqui Moly were fastest mover by mechanics...whatever. So here I am back again. I read about BG 44K and B-12. I even called Bosch to see if I could find out what metal they use for their sensor. The guy said no info available. Sooo I am leaning to a Delphi because of GOLD compound but the replacement will cost me $275 including labor . I read where some had to put in a follow up of Techron .. I was going to modify /cheat the resistance in the harness to shut up the PING..but then I saw the wiring diagram of the sensor assembly and noticed how it was engineered. A little more complicated the way the float rod contact connects to the sensor wire resistor. *****Bottom line...looking for the best cleaner to get rid of sulfur contamination.

 

[zzyzzx]

1999 Oldsmobile Alero. Also having this issue but not nearly as bad. Only happens if I let the fuel level go below 1/4 tank. Supposedly the fix is to replace the sensor but would have to drop the tank to do that and not sure that I want to do that just to replace the sensor when I have a mostly working gauge and a trip odometer. Now if I ever need a fuel pump I would do it,

 

[Rhymingmechanic]

My 2001 Silverado fuel gauge got flaky a few years ago. It would suddenly swing to E and trip the low fuel light (sometimes right after a fillup) among other strange behavior. Eventually, it would read E and set off the light when it was near empty, but I used the trip odometer instead of trusting the gauge. Multiple Techron treatments didn't change anything.

The fuel pump had to be replaced a year ago, and the gauge works again. Low fuel comes on closer to 2.5 than 3 gallons now.

Does your car have a fuel pump access panel? If Techron doesn't work, that would make it easier to change or clean the sender. Otherwise, use the odometer and live with it if you don't want to drop the tank. That was more of a job than I wanted to try on my pickup.

 

[cartech]

My 2001 Silverado fuel gauge got flaky a few years ago. It would suddenly swing to E and trip the low fuel light (sometimes right after a fillup) among other strange behavior. Eventually, it would read E and set off the light when it was near empty, but I used the trip odometer instead of trusting the gauge. Multiple Techron treatments didn't change anything.

The fuel pump had to be replaced a year ago, and the gauge works again. Low fuel comes on closer to 2.5 than 3 gallons now.

Does your car have a fuel pump access panel? If Techron doesn't work, that would make it easier to change or clean the sender. Otherwise, use the odometer and live with it if you don't want to drop the tank. That was more of a job than I wanted to try on my pickup.

No access panel. My wife uses the van and I am thinking of blocking the 2 wires of sensor to shut the PING off. Will talk to a few mechanics too, to get their input.

 

[cartech]

1999 Oldsmobile Alero. Also having this issue but not nearly as bad. Only happens if I let the fuel level go below 1/4 tank. Supposedly the fix is to replace the sensor but would have to drop the tank to do that and not sure that I want to do that just to replace the sensor when I have a mostly working gauge and a trip odometer. Now if I ever need a fuel pump I would do it,

One of my thoughts is to get at the fuel pump , just to clean off the sensor with BRASSO or whatever, since it lasted 2 years with gas on it.