Fuel gauge going crazy

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.

my gas gauge began bottoming out about one yr ago and after i drove approx 50 miles it would raise back up and register correct but about 2 weeks ago my gauge began to register full all the time unless i am in park. i don't know if the fuel pump is trying to go out or if it is a sensor in there. can someone please give me some advice about this.

You may want to start a new thread as this one is kinda old. You did not say what vehicle/year you have the problem with. Knowing that will help others help you out.
More than likely your sending unit is shot. The decision you have to make is, is it worth it to replace it and/or the whole pump assembly now or wait until the pump goes out. Read the posts above and that will give you a pretty good picture of your choices. Good luck.

I recently removed my pump/sending unit. Test with OHM meter showed intermittent readings due to wear in the plastic float hinge. I removed the brass hinge pin and used solder to slightly increase its dimension to take up the wear in the plastic. Retest with meter corrected problem. This repair was done on a 2000 Buick La Sabre with pump access in the trunk, 1.5 hr. Sure saved a lot of money.lol

My fuel gauge went crazy about 6 months ago. My gauge read full or nearly full all of the time. I've been using my trip odometer to keep track of the fuel. I can always get 300 miles out of a tank. But what a hassle if I accidentally reset the trip odometer. I decided to fix it.

I posted a step by step guide on how to replace the fuel level sensor on my site with pictures. have a look

http://www.redhouseon7th.com/redhouse/howto/2010BuickFuelLevelSensor/index.html

"2005 Malibu Fuel Level Sender Fix - Beating the System

One day the fuel level sender in my 2005 Malibu failed, fuel gauge to alternate between full and empty and causing my
check engine light to come on. I chose not to fix it for a while - given the
cost and hassle - and just calculate fuel use by mileage. I figured,
why bother going through all the hassle of dropping the tank and
changing the sensor if my fuel pump is still good?

Well, some months passed and the car came due for inspection. I live
in Massachusetts and to get the car to pass inspection, no error codes
can be present in the computer. Here's what I did to make it pass
inspection for under $2: Trick the computer with a 100ohm 1/8 watt
resistor from Radio Shack. Here's how I did it:

At the fuel tank electrical connector block under the car near the
tank, find the purple wire (fuel sender) and the black wire (ground).
In the back of the connector (the side which leads up to the front of
the car, NOT the side that leads to the tank), take a sewing needle or
small awl and clear paths for the resistor leads to slide in past the
wire seals and make contact. Carefully slip the 100ohm 1/8th watt
resistor into the spaces next to the wires, connecting the purple and
black wires with the resistor. Next, open the connector and check with
a multimeter that there is continuity between the connector pins and
the resistor leads on the back of the connector. Reconnect and turn
the key to the on position. The fuel gauge should now be reading about
1/4 tank - a reading it will have permanently. To finish the job, put
some RTV silicone on the contact points of the resistor and plug to
keep water out. Blast the code from the computer if you want. If you
ever change the sender, remember to take the resistor out!

Disclaimer: Enjoy this cheap fix, and understand that I take zero
responsibility for the information, and do not recommend that you
actually do this."

Keep it real,

-M@

Same problem with my Mom's '05 Malibu. I drove her car yesterday and didn't experience any problems, but she says the fuel light comes on, the bell 'dings', and the guage can go up and down erractically.

But get this - a garage failed her on her inspection because of this. And now they want to charge her $300+ to replace the sender.

Ever heard of being failed on a state inspection because of a bad gas gauge? This is Massachusetts. When I lived here I thought it was only about emmissions and safety. How is a broken gas gauge either of those things? I don't think it is. I think the garage is just trying to force her into an unnecessary repair. My mom says this problem has existed for a couple of years now but because her driving pattern is SO predictable, she really doesn't NEED to repair the gauge. It was only noticed on THIS inspection because she mentioned it in passing.

She's also a senior on a fixed income, so she'd rather not outlay that money unless she absolutely HAS to...