I just bought a C5 Z06 and I had a 3 hour drive from the dealership. about an hour into the drive, with a full tank, my light came on to check the gauges and my tank said it was empty. when I first start the car it reads normal, but its usually around an hour drive when it says its empty even after I just filled up

 

I have this problem also. From what I read, its pretty common issue. I believe its the fuel sender unit? Someone correct me if Im wrong

Bugs me, one day Ill fix it

 

I had the same thing happen to me when I bought my z. Just like you on my way home from buying the car. Anyways, you can find plenty of threads on this problem on here. What works for me, and others I believe is techron, I usually add a bottle every few fill-ups and the gauge has been working fine.

 

sensor in tank gets a build up on it. Sometimes a additive can clean it. Otherwise it needs to be replaced. It's a big job. Tank needs to be dropped.

 

Sticky fuel sending unit, when I used Shell it would stick a lot but since I switched over to Chevron, I haven't seen it lately. Stick to Chevron and you should be good but reset your trip and keep an eye out just in case because it sucks pushing your Covette to the side of the road when you run out of gas. Ask me how I know.....

 

Run a couple of bottles of Techron through the tank and see if that clears it up. My understanding is the sending unit is sensitive to sulfur in the fuel, so watch what kind of gas you are using.

 

Just use Texaco or Chevron and you will not have the problem again. When my gauge went to empty I put in Techron for a couple tanks and then the gauge started working again.

 

Techron bottles and Chevron or Texaco Premium to the rescue!

 

Hang on! The OP states he just bought the car from a dealership.

Did the car come with any kind of warranty? I'd notify them immediately as the car had issues mere hours after you bought it. It is generally a fuel sender unit and as others have stated, there is plenty of reading on the subject. If there is any kind of warranty, the dealership should fix it. If the dealership won't help, try the Techron route.

What year is your car? You don't have to drop the tanks if your car is a mid '03 or older. If newer, then I agree you will need to drop the tanks.

Lastly, welcome to the forum. There are plenty of people who can help you with diagnosing / fixing your car. If you're the least bit handy, you can do quite a bit of your own work and save a considerable amount of $$$$. As an example, if your car is a mid '03 or older, the level of difficulty replacing the fuel sending units is about equivalent to changing a tire.

 

Can you explain how its done on the older cars?

 

I had same problem with my 2002 ZO6. Use only chevron premium gas and put techron about every 2 months. Worked find for a while . I needed some work done on my car took it to the dealer here in grapevine tx. Told what was going on and thought was a sending unit and have them change it out. Long story short was not sending unit but gauge cluster. Saved me about 1200 dollars. A lot of info I read was pointing in that direction to change the sending unit.

 

Below is the description I had posted some time ago. Hope it helps.

The process is actually fairly easy. I have a 2003 Z06 non FFS system so the process should be similar if not the same.

1) Run or empty the tanks down as close to empty as possible. I drove mine to get the fuel level down. I used my odometer to track my mileage and then had a gallon can of gas in the car in case I ran out. (didn’t need it)
2) Disconnect the battery
3) Jack the rear of the car up and remove rear wheels (remember to chock the front wheels and use jack stands)
4) Remove the aluminum cover on the rear of the tank (IIRC one nut and one bolt)
5) Disconnect fuel lines and electrical connector
6) Remove the six bolts holding the fuel pump assembly
7) Remove fuel pump assembly. I recommend starting with the right side (passenger side) to become familiar with the process. The right side is the siphon / jet pump side and will easily slide out of the opening. For the left side, you have to detach the fuel sending unit to allow the float rod to line up against the side of the fuel pump. (white plastic base is clipped onto the metal housing) The opening is just large enough for the fuel pump to fit through with the float rod pressed against the fuel pump body.

The process is very straight forward and will take a couple of hours at a relaxed pace. Now that I’ve done it, I could probably do both sides in an hour. It doesn’t require a lift or any special tools.

Two things. 1) I don’t know if sending units are sold separately from the pumps anymore. My car had 199,000 miles on it so I decided to replace the fuel pump assemblies on both sides (pumps were original). 2) Inspect your purchases closely before tearing your car apart. The fuel sending unit I had for the left side had a small plastic piece broken rendering the unit inoperable. Fortunately I have more than one vehicle so I could leave the Vette apart for the 3 days it took to get a replacement.

 

Thanks for posting. I am able to find the left hand sending unit only but not the right, although I read somewhere that they are the same. If true, I don't know why the ones I find for sale specify left hand. My car has 150,000 miles with original pumps but they still produce correct fuel pressure so I see no need to replace them. Especially if its this easy to do when they finally do go. My car had the gage problem when I bought it nine years ago. The Techron cleared it up for a few years but eventually stopped working. Again, thanks for posting.

 

To 3sAcrowd, thanks for posting the procedure. My 02Z is having this problem, and the techron stopped working.

 

Mine drops to empty every time I fill it up. Stays on empty till I run maybe a gallon of gas out. Then it goes back to full and acts normal till I fill it again. I've used Techron numerous times and it hasn't helped. Since it only does it when it's topped off I'm not too worried about it.

 

My 02Z gauge starts getting erratic just around 1/2 it works just fine 1/2 and above.

I have had c5's do this running techron and shell gas cleaned up the sender.

On this car I just use the 1/2 mark as my time to fill the tank, I keep my odo set to trip A when I get up near 300 miles I know I better get fuel, usually about 10 gal fills it.

You can try shell fuel and techron if it cleans it all well and good if not there is a gas gauge removal in your future.