JBoyle997

So I searched the forum but it seems that everyone has a different type of gas gauge issue then I do. My gas gauge never dropped to zero. I filled the tank up, and as time went on the gas gauge just stayed pinned at about a little over half a tank. I finally realized that i cant possibly still be at that level of gas since i had driven a good amount. So i went to go fill up the tank and the car would only take about 5 gallons of gas. The gas gauge moved a tiny bit towards full and thats it. I turned the car on and off a few times, and the gauge is still pinned at a little over half a tank. I tried a bottle of Techron, and drove around for about an hour. Gauge is still stuck. Any thoughts?? JB

racebum

you need to cycle through a few cans of techron

sensor contacts are probably grimed from sulfur

40oz of techron on a full tank, drive, when it gets to 1/4 add 20 more, then refill, should be back to normal

if it isn't you may be replacing the sending units

JBoyle997

Ok, thanks racebum I will try that out. Thanks for the help.

Z06ster

The root cause for the problem you are having is that the C5 Corvette is notorious for accumulating sulfur deposits on the circuit board that modulates the mechanical fuel level information from the tank floater to electrical information. These circuit boards cannot be purchased separately. They are part of the entire fuel sending assembly. There are two, one in each gas tank (The C5 has two fuel tanks, one behind each seat). Many on here swear by the Techron solution. Definitely try it first. But, if techron fails, you will need to replace one or both of the fuel sending assemblies. The dealer has way to test if one or both are bad.

Ever since I had mine replaced, I only use Chevron fuel in my tank and have never put anything else.

JBoyle997

Thanks for the help. I'm in NJ and there are no Chevron stations anywhere near me. The last gas i put in before this problem started was Sunoco. Not to say that had anything to do with it, i always run super. Is there a second best to Chevron gas in my area that you guys recommend? Once i get this problem fixed i certainly don't want it to re-surface. I'm no mechanic so i guess this is going to cost me if the Techron doesnt work. I just bought the car about 2 months ago, I love it. 62k miles.

3sACROWD

I'd suggest pulling your codes. You will likely see P0461 or P1431. My guess is it will be P1431.

Here is an excerpt on how to do it.

READING YOUR C5 Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.

There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.

Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.

Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!

NOTE!!! Start the car and let it idle. Then take it for a drive and cause the problem to occur. When you return home pull the codes BEFORE you shut off the engine.

racebum

you have a shell or conaco phillips?

they both have top tier low sulfur gas

fxdl

Sulfur maybe but I have suspected for a long time its that damn ethanol. My fuel guage never reads full. When it is full its at about 7/8 on the guage. Sometimes it doesn't work at all. I just set the A trip odometer every time I fill up so I know where I'm at with fuel. I suspect I'll be putting new sending units in eventually but no hurry. I assume you have to drop the drivetrain to get the tanks out right?

racebum

not on a pre 2003 car. they slide right out the side of the tank

you do have to drain the gas tank but it's not that bad of a job

from what i hear the worst part is twisting the new sending unit into the tank without bending it

Z06ster

It sounds like there is good gas out there in New Jersey. But, if you are really worried, you can always add a bottle of Techron to your fuel tank periodically.

As for the cost of replacement of the fuel sending unit assemblies, parts and labor at the dealer are around $1000 I believe... that's for both tanks.

bikeriderga

Clear the DIC codes, put in a bottle or two of Techron, and run Chevron/Texaco is the best cure.

I always had problems on my 00 Coupe when I used something other than Chevron or Texaco. Shell seemed to come in 3rd.

Worst were BP, Conoco, and the no name stations.

racebum

sulfur content and gas tier can be found online

BP is what you would call cheap gas but conoco is not

JBoyle997

Well I hate to run the car completely out of gas but my plan now is to keep a can of gas in the car wait until its empty then throw another bottle of Techron in and fill it up again...see if the gauge moves. I will remember this time to reset the odometer. I will also check out the codes thanks a lot for all the great info.