Fuel gauge goes Empty after half !!
Safety Car
Joined: Jul 2004
Posts: 3,904
Likes: 29
From: Vancouver Washington
I just finished with this exact problem. I've had it in the past and a few bottles of Techron Plus has always fixed it. This time it was so persistant I figured I was going to have to change the sensors. The car had sat for a month while I put a new engine in and the problem was there as I started to put the break in miles on. I put 3,000 break in miles on, 7 or 8 tanks of gas, and each time I filled up I used a "Treats 20 gallons" bottle of Techron Plus. Finally today the guage started working properly again. Good luck with yours.
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
I can't believe you've been a CF member since '06, and don't know about the fuel gauge problem.
Seriously, it's probably the most common issue (of many) for the C5. About 7 years ago, I switched to Chevron gas, and the problem went away for good.
Seriously, it's probably the most common issue (of many) for the C5. About 7 years ago, I switched to Chevron gas, and the problem went away for good.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
It comes up regularly. In your case it's working initially with a full load so the sender must be OK at the top of its range.
Here's a copy of a recent post I made:
I'd recommend that you don't run the car low on fuel. If you keep it topped off the sender which causes the problem will always be submerged and the chance of deposits building up may be less. Techron should work if you give it time but if not, you may be looking at changing the senders. If Techron hasn't cleaned them it means they must be badly fouled. There are DIY threads here if you end up going that way.
Normally the symptom is that it will fall to zero. In my case, the first time it happened I filled to full but the gauge showed 3/4 and slowly rose to full. I treated it quickly and it cleared. I've since had a "drop to empty" when I ran the tank low on one occasion.
You can see from this picture how the sender works. The floating arm runs over pick offs and depending on the amount of fuel sends a different resistance to the computer to gauge the gas. The right tank pumps fuel to the left from where it feeds the engine. The computer averages the contents of both tanks. The problem is that sulfur in the gas fouls the pick offs causing a bad reading.
The easy solution is to treat it with Techron (or some prefer Seafoam). If it's only slightly fouled Techron will clear it quickly. If it's been a while with those symptoms and it's badly clogged it may take a number of treatments to clean it. If it's really badly fouled you may have to replace the senders. Theres one in each tank.
Try Techron first. The other thing to do is to check the codes and clear down any fuel related problems.
Report back but give the Techron time to work
Here's a copy of a recent post I made:
I'd recommend that you don't run the car low on fuel. If you keep it topped off the sender which causes the problem will always be submerged and the chance of deposits building up may be less. Techron should work if you give it time but if not, you may be looking at changing the senders. If Techron hasn't cleaned them it means they must be badly fouled. There are DIY threads here if you end up going that way.
Normally the symptom is that it will fall to zero. In my case, the first time it happened I filled to full but the gauge showed 3/4 and slowly rose to full. I treated it quickly and it cleared. I've since had a "drop to empty" when I ran the tank low on one occasion.
You can see from this picture how the sender works. The floating arm runs over pick offs and depending on the amount of fuel sends a different resistance to the computer to gauge the gas. The right tank pumps fuel to the left from where it feeds the engine. The computer averages the contents of both tanks. The problem is that sulfur in the gas fouls the pick offs causing a bad reading.
The easy solution is to treat it with Techron (or some prefer Seafoam). If it's only slightly fouled Techron will clear it quickly. If it's been a while with those symptoms and it's badly clogged it may take a number of treatments to clean it. If it's really badly fouled you may have to replace the senders. Theres one in each tank.
Try Techron first. The other thing to do is to check the codes and clear down any fuel related problems.
Report back but give the Techron time to work
Last edited by DeeGee; Oct 2, 2010 at 04:04 AM.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
Both senders can be affected as its caused by sulfur build up.
Melting Slicks
Joined: Dec 2003
Posts: 3,315
Likes: 17
From: Near Jacksonville Fl.
I was experiencing fuel gauge drop out on occasions so when I had my fuel pump out earlier this year.
I was changing over to a Racetronix pump so I cleaned the 1 dark spot I had on the drivers side sending unit with electronic contact cleaner and the small brush on the end of the can.
So far it's worked like a champ, no more drop off at all for the fuel gauge.
I was changing over to a Racetronix pump so I cleaned the 1 dark spot I had on the drivers side sending unit with electronic contact cleaner and the small brush on the end of the can.
So far it's worked like a champ, no more drop off at all for the fuel gauge.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,448
Likes: 21
From: EARTH
THANKS for the replies guys. 
Well I never had the problem so I didnt search the subject.
Well I never had the problem so I didnt search the subject.
Administrator
Joined: Mar 2001
Posts: 368,297
Likes: 24,776
From: In a parallel universe. Currently own 2014 Stingray Coupe.
C7 of the Year - Modified Finalist 2021
MO Events Coordinator
St. Jude Co-Organizer
St. Jude Donor '03 thru '25
NCM Sinkhole Donor
CI 5, 8 & 11 Veteran
Try the Techron in the gas tank - it has worked for many other owners before.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
If the orifice in the R/H tank siphon pump becomes restricted/blocked, you will run out of gas on the L/H tank and be stuck on the side of the road.
The replacement fuel module assy. from GM has an "improved" sending unit card (circuit board) and no longer uses a "tea bag" style fuel strainer on it like the earlier C5s had.
I had to deal with this recently.
P.S. The GM part number for the R/H fuel module assy. (combined fuel level sender and siphon-jet pump and comes with a new gasket and screws) is: 89047746
The replacement fuel module assy. from GM has an "improved" sending unit card (circuit board) and no longer uses a "tea bag" style fuel strainer on it like the earlier C5s had.
I had to deal with this recently.
P.S. The GM part number for the R/H fuel module assy. (combined fuel level sender and siphon-jet pump and comes with a new gasket and screws) is: 89047746
Last edited by LoneStarFRC; Oct 4, 2010 at 11:31 AM.
