Hello to all ....I have read all the material on the issue with this car.... I have read until my eyes are bleeding.... I have had multiple problems with this car the fuel gauge keeps showing empty/I have replaced oil sending unit and I have replaced both fuel sending units. I am now thinking its the computer I have had a friend put a used computer on it to help see if that was the issue (twice) .When this car gets to a quarter of a tank ....gas gauge reads empty.

 

Run some techron fuel additive in there, and that'll go away after a few tries. I know, because mine was never reading full for years. Then I tried this and it fixed it. I use Shell Gas. Exxon seems to not work for me.

I always do it when the tank is low (1/4 left or less). It is going to take a few shots before this works. Do one at a time. Then fill up. Rince, repeat. I think this happens because our fuel system never could have imagined we'd have a blend of ethanol. But that's my guess.

 

Not sure what you mean about oil sending unit on the other side, there is only one. Did you mean fuel sending unit?

With regard to the fuel sending units, it is not the computer, it is the sending units themselves. The potentiometers get messed up by contaminants like sulfur in the fuel. This is made worse by the fact that the right tank empties first, by transfer to the left tank, and when the computer senses the wrong sequence, it will drive the gas gauge to zero as a warning. Of course, the transfer itself can also fail. I ran out of gas once that way, thinking it was just a sender problem.

Techron may help, as mentioned above. I believe it is more useful as a preventive than as a fix when the senders get real bad. Sometimes it is necessary to replace a sender.

 

I would do as VetteFTW recommends. Run a 20 oz bottle of Techron in a full tank of gas. Repeat until gas gauge reads correctly. I would do this up to 4 times before I'd even think about replacing the sending unit.
I had the issue with my 98 and Techron solved the problem. Now I run an occasional bottle in all my Vettes.

 

Be patient with the Techron. It took me over 1,000 highway miles, and 4 or 5 bottles of Techron and Shell Invigorate pump gas Premium before mine started working right again!!

 

My fuel gauge goes to empty when I hit a bump sometimes. When I restart the car it goes back to normal. I'm going to try the Techron.

 

I may have been confusing last time due to total frustration with this car. I have now replaced both fuel sending units and the oil sending unit I still get the same response( empty fuel gauge) the car is not empty and I am now thinking computer. Any suggestions?

 

Hello ALL.....I have replaced the oil sending unit and both fuel sending units. I am still have the same issues *tank full reading empty* I am now thinking computer.Thanks for advice..... I am still working on it.

 

Or, since I have to run the car on premium anyway, I run Chevron Supreme, which already has Techron in it.

In a related issue, crappy gas can cause the Malfunction Indicator Light aka check engine light to go on, to quote my 1999 owners' manual.

 

Or just the crappy engineering by the Chevy. not so brilliant designers You cannot repair a faulty design problem with replacing with the same stuff. It will happen again. Never had a gas gauge issue in any of my cars until the Vette. Have instituted work around issues so I do not run out of gas should the gauge not perform right.

 

I'm with you on the engineering. Many things on the C5 seem to fail far earlier in the vehicles life than on any other vehicles I have ever owned, and at 67 years old, I've owned my share.......

 

Use a 20 oz bottle of Techron or a can of Seafoam when the gauge jumps to empty. Even using Top Teir gasoline I still get the dreaded fuel gauge empty occasionally.

A bottle of Techron or Seafoam will get the sulfur deposits on the sending units to dissolve. Only car I ever had that has this problem.

PS DON"T USE TECHRON AND TECHRON TOGETHER.

 

As the 'new' owner of a pre-owned 1998 Coupe with 88k miles, I am curious about the fuel tank level sending issue.
I also used to own a 2003 Saturn VUE that also had two fuel tanks and emptied from the right (passenger) tank first.
The salesmen used it as a selling point that 'the twin tank system was originally designed for a Vette'.
You mention in the thread that the software gives an indication of 'EMPTY' when the sending unit sequence is not as expected.
Does this software also throw a code on the Driver Information Center (DIC) when it encounters this error?
If I remember correctly, if the Saturn had this condition it would throw a code and flash the fuel low warning light.
If no DIC code is thrown, then it appears the software engineers learned from their earlier mistake when they coded the 2003 Saturn VUE fuel system.

 

All, The C5 will aid you in finding the fault in your fuel level system via the DIC.
In general, the very first step in troubleshooting a C5 issue is reviewing the DIC codes...

Way forward>
Review the DIC for fault codes, write them down for posting to this thread as the car sits now...After recording/documenting all DIC codes, clear all codes.
Take the car out for a drive until the fuel level system faults, review and record/document all DIC codes again for posting to this thread.
To Summarize,
Post> Pre-Drive DIC Codes.
Clear Codes
Post >Post Drive Codes.

Note there is a lot of technical talent on this CF board that have been around these C5's for many years and most often the CF board can provide you great recommendations to solve your issue.
Cheers,
Goose

 

Fail far earlier? These cars are 17-23 years old.

 

Do you mean Techron and Seafoam together? And why?

 

???????

 

Some of the failures happened just before, and just after, the factory warranty expired. The factory warranty on mine was 36months/36,000 miles, a far cry from 17 years, and an even farther cry from 23 years. Just because something just failed (again, I might add!) doesn't mean it's the first time it failed. Really, how many vehicles have you owned with fuels sending unit problems? I'm 67 years old, and have owned a LOT of cars. Never had a problem with any of the sending units/gauges in ANY car I've ever owned, except my C5....

 

@rrwirsi - I remember doing my first long trip with the C5. After reading problems with gas gauge inaccuracies, I just kept filling up every hour, sort of took the enjoyment out of the touring experience. But I did prove that my gauge was accurate and now have no more worries regarding that issue.
@ grinder - Nor sure how long you've had your C5, but I have gone from "how do I repair" to "do I need all of this complexity?" My car is 20 years old and from that perspective, it's unreasonable to ask for no failures. And obsolescence comes with progress, just as discontinued parts help keep Giant Motors from getting crushed under its own weight.. The complexity (horn only, lights only, horn and lights, passive, active, really?), added to age and discontinued technology is what frustrates a lot of recent owners of the earlier versions of the C5. I haven't even mentioned EBCM....

What I do look forward to is not how to fix the component (it will break again) or even adapt newer components from later C5s or C6s (which may soon also be obsolete/discontinued), but a successful de-cluttering and simplification of the systems in the car. I don't expect any agreement from purist owners who worship quaint design philosophies or technicians who have the time, tools and brains to keep even steam cars on the road. But I do think there is a group out there who like the styling of the C5 and would like to be able to use it as a daily driver if they so decided. My car is alright and emissions-legal right now, but when the next big problem comes around, I may have to start the lobotomy.

 

I hear you on simplifying things. Back in the 60s and 70s, sliding levers that were attached to cables worked just as well, and were more reliable, than the electronic junk of today. I just shook my head when I saw that the newer Corvettes cannot use full throttle until some module let's the PCM know the tires are now up to normal temperature (at least, what some engineer THINKS is 'normal', and has programmed that value into it!), so full throttle is now available!!! It's like these young "I'm gonna change the world for the better" electrical engineers from company "C" are trying to outdo the young electrical engineers from company "F" with the fanciest crap they can think of!! This is all at OUR expense, and inconvenience. In my opinion, Corvette owners usually hang onto their cars longer than Nissan Sentra owners do. So yes, I expect things to go wrong in 10, 15, or 20 years down the road. For the group of Corvette buyers that lease, and get a new one every 3 years, unexpected failures may be inconvenient, but at least repairs are under warranty. But WAY too many things fail on these cars long before 10, 15, or 20 years on. I guess I'd sum this up with a friend who lost a stock LS7 engine at 44,000 miles. Yeah, it was off warranty, but I think most car owners would expect you wouldn't need a new $15,000.00+ engine in that mileage. Especially car owners who paid over $75,000.00 for their cars. Or the C5 owner whose car was only a little over 3 years old when the steering column locked, and damn near killed him 1,400 miles from home. Yes, they have locked while being driven. How long has GM been building locking columns? Since the late '60s, I believe. But they never had any problems like this until the C5 came out. I love my 2000 Vert. But it sure could've been more completely thought out before being released to us, the public. I digress.....