When I fill up my fuel tank in my 2005 malibu the needle will go past F and then start dinging and fall to E and then the engine check light comes on. Once you drive some gas out of the tank the check light will go out and the needle will go to where the fuel level is at. After a while the needle will start going crazy. half a tank will show full, quarter of a tank will show half full.

Have a similar problem with my S-10. Could be a ground wire or a connector. Very good chance its your sending unit. Usually these are part of the fuel pump assembly. In my case, I can live with it by just keeping track of the mileage. In no mood to drop the tank and pull the pump unit to replace just the fuel level sending unit...at least not till the fuel pump actually goes out. But do take the time to check the wiring.
Good luck.

I don't think its the wires. On the fuel pump there is a sending unit that sends the signal to the gauge for the level of fuel. That could be on the fritz. On most cars you can get it seperate from the fuel pump. Something to look into. You can check the ohms reading from the sending unit.

Its either the sending unit that is messed up or the cluster.

I think if you do a quick check of AllData, or Autozone for a parts description, the fuel level sending unit is a part of the fuel pump module for this vehicle. It would require dropping the tank to get at that. In the trouble shooting guide of the Auto Repair Reference database for guage problems it states:
Gauge operates erratically


Check for loose, shorted, damaged or corroded electrical connections or wiring and repair as necessary.
Check gauge sending units and replace as necessary.
At a dealer or service center this is not a cheap fix. Like I said on my S10...I just do the math.
Good luck!

Actually, I believe the fuel pump module is accessible through the back seat or a panel on the trunk floor of a 2005 Malibu (like the Bonnevilles and Buicks). The gauge sending unit is highly suspect in this case.

depending on the model you can get the sensor seperate. But I need the vitals to find out. What is the model and what engine size.

Actually, I believe the fuel pump module is accessible through the back seat or a panel on the trunk floor of a 2005 Malibu (like the Bonnevilles and Buicks). The gauge sending unit is highly suspect in this case.

most newer cars are like this, but I am not sure on the newer malibus. Never worked on one. Couldn't tell you.

You may be interested in the following:
Fuel gauge: The engine may not start or may stall because the tank is empty yet the gauge shows fuel remaining, or the fuel gauge will not show full after refilling due to sulfur corrosion of the fuel level sender and if after treating with Fuel System Cleaner PLUS the problem remains, the sender may need to be replaced. (2004-06) ConsumerGuide; Malibu Technical service Bulletins
Notice that it says the sender may still have to be replaced. I think if you search this forum for "Fuel Pump, or Fuel Filter" you will find the metod of repair is dropping the tank. Try this link;
http://www.automotiveforums.com/vbulletin/t896225.html (http://www.automotiveforums.com/vbulletin/t896225.html)

As far as cost, you could simply stop by a dealer to confirm the location of the sendng unit and get an estimate.

I found this on Edminds. Its a 2003 but with a similar problem to yours:
http://townhall-talk.edmunds.com/direct/view/.f16047e/30
I have a 2003 Chevy Malibu with 76,000 miles. The fuel sensor needs to be replaced (as verified by a dealership test). The dealership cost is $540. (The high price is due to the labor involved in dropping the tank.) A local garage will replace the entire fuel pump for $500. They say GM pumps have a "gold" metal that gets eaten away by gasoline. They say a Carter pump is better, cheaper, and will last longer. My questions: Should I just replace the fuel sensor, since that's the only problem right now? Or should I replace the fuel pump while the tank is dropped, with the assumption that the pump is nearing the end of its life?

Interesting find. Probably 500 parts and labor. To me, I believe that is way too much money. Get the sensor, replace it yourself in the drive way. I doubt there is any gold on the sensor itself, but w/e that person wants to believe.

The original poster did not say how experienced he was with car repair. Given the information in the Tech Bulletin for this type of problem, it may be worth a shot, for a few bucks, to run the fuel system cleaner first. Of course that may not solve the problem but it is not very expensive and is certinly not a difficult task.
However, while the sensor unit may be a replaceable part, droppin the tank just for that may not be worth the trouble. Doing it in your driveway, not up on a hoist just adds to the fun. Besides, opening the tank and pulling out the pump assembly runs the risk of damaging that or getting debris in the tank. If it were me ( and as I mentioned I have the problem on an S10) I would wait until the pump fails.

I don't know about the "gold coating" but the mechanic I talked to said the corrosion is not uncommon.

Some cars it is necessary to drop the tank, others you can do by removing the back seats, or the spare tire area. As far as fuel cleaner goes, the Sending Unit is probably already done. I don't think that fuel cleaner is going to help. But if you must, get a product called Bg 44K works like a charm for cleaning the fuel system. There is not a better product out there.

IIRC, there is nothing under the rear seats. You will probably have to drop the tank in order to do it. As far as contamination, you just need to clean the area around the pump really well before removing it. So clean that up and get a new pump gasket. You need to get the individual prices of the pump vs the sender. My suggestion. Go to www.rockauto.com (http://www.rockauto.com) for parts. They are cheap and very reliable. 95% of people on my other (way more trafficed forum) have used them. They are excellent w/ customers and have outstanding prices. Worth looking into.

I had the same problem on my 05 malibu I dropped the tank yesterday[not a big deal] & pulled the pump out, the fuel level sensors are known to fail one of the tiny metal legs on the sensor was broke on mine, like I said it was doing exactly like yours. Don't do like I did & put a used one in. It looked fine but it doesn't work right either I guess a bought lesson is the best kind.