Gas gauge shows empty when I have 1/2 to 3/4 tank. Above and below that reads fine. I have tried 5 bottles of techron on full tanks. No luck. Any suggestions?

 

Check for corroded ground wires.
PM Bill Curlee, he can tell you which ground to check for the fuel sending unit...

 

Thanks

 

VERY common issue.

Always reset your mileage trip when you refill so that you can tell how many miles are on the tank.

 

Yes so I hear!

 

Indeed this is all to common. Here is what is going on...

The C5 has two rear fuel tanks. Inside each fuel tank, there is a "fuel sending unit". These units are actually assemblies, made up of several parts. The job of these is to provide the correct electrical signal to the fuel gauge. How does it work? There is a floater in each tank that has an arm on it. As the arm moves with the level of fuel, it moves along an electrical contact board that has several electrical traces. So basically, the mechanical movement of the arm is modulated into electrical information which is ultimately sent to the guages. Due to a corrosion process, these electrical traces become defective. Sorry Techron/Seafoam fans, add all the additive you want, this will not reverse the corrosion on the traces, although it is fair to say it will help it from getting worse. Given this, I ONLY put Chevron gas in my car.

Unfortunately, this is a known problem by GM and they have a TSB (technical service bulletin) about it. If you really want to address this, you can go to the dealer and they can perform tests to determine if the fuel level sensor is bad in one tank or both. I believe you would pay somewhere between $150 and $200 for this evaluation. Keep in mind that while it is really only the fuel level sensors of the fuel sending units that go bad, I think GM just goes ahead and replaces the entire sending units... and that's in part what makes this repair expensive.

I had this repair done a few years ago and my gas gauges read absolutely great.

 

Z06ster is right. If you've tried the sea foam or Techron that many times the sensor is dead. The reason some of us have made it work is that we caughjt it in time. It starts with sulfur build up on the sensor. If you catch it early the Techron cleans the deposit off the sensor and it starts working again. At some stage the build up becomes so bad that the cleaner cant get reid of it. At that stage its a sensor change.

This thread has some good pictures:
http://forums.corvetteforum.com/c5-g...k-sensors.html

Heres the procedure from the book. PM me if you want the one with pics. Guys who haver had it fixed at the dealer seem to pay about $500.

Document ID# 776239
2002 Chevrolet Corvette
________________________________________
Fuel Sender Assembly Replacement W/O FFS
Tools Required
• J 34730-1A Fuel Pressure Gauge
• J 37088-A Tool Set, Fuel Line Quick Connect Separator
Removal Procedure (Left or Right)
Caution
Before servicing any electrical component, the ignition key must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.
1. Disconnect the negative battery cable.
2. Relieve the fuel system pressure. Refer to the Fuel Pressure Relief Procedure .
Caution
To avoid any vehicle damage, serious personal injury or death when major components are removed from the vehicle and the vehicle is supported by a hoist, support the vehicle with jack stands at the opposite end from which the components are being removed.
3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
4. Remove the rear wheel and tire assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
5. Clean all of the fuel connections and the surrounding areas before disconnecting the fuel pipes in order to avoid possible contamination of the fuel system.
6. Drain the fuel tanks. Refer to Fuel Tank Draining Procedure .
7. Remove the fuel tank shield.
8. Mark or identify each fuel pipe in order to aid in installing the pipes in their original positions.
9. Disconnect the quick-connect fittings from the fuel sender. Refer to Quick Connect Fitting(s) Service (Plastic Collar) .
10. Cap all of the fuel pipes.
11. Disconnect the fuel sender electrical connector.
12. Remove the fuel tank strap.
13. Support the fuel tank.
14. Remove the fuel sender attaching bolts.
15. Remove the float arm retaining clip and the float arm for the left fuel sender only.
16. Carefully remove the fuel sender with the gasket.
17. Clean the gasket sealing surfaces.
Installation Procedure (Right)
1. Inspect the fuel sender gasket for damage and replace if necessary.


Important
Do not bend or twist the float arm.
2. Insert the float arm through the fuel tank opening.
3. The fuel sender may need to be rotated in order to facilitate the installation.
4. Align the fuel sender gasket tab (2) with the fuel sender cover mark (1).
5. Align the fuel sender cover mark (1) with the fuel tank mark.


Pic 2
6. Hand tighten the fuel sender attaching bolts until finger tight.
Notice
Refer to Fastener Notice in Cautions and Notices.
7. Tighten the fuel sender assembly attaching bolts in sequence.
Tighten
Tighten the bolt to 7 N•m (62 lb in).
8. Connect the fuel sender fuel feed pipe (1) (from the jet pump to the left tank, and the fuel feed rear crossover pipe (2) from the left tank to the jet pump). Refer to Quick Connect Fitting(s) Service (Plastic Collar) .

See Pic 2

9. Connect the fuel sender electrical connector.



Pic 3


Pic 4
10. Install the fuel tank strap (3).
11. Install the fuel tank strap bolts (1, 2, 4).
Tighten
o Tighten the bolt (2) to 25 N•m (18 lb ft).
o Tighten the bolt (1) to 25 N•m (18 lb ft).
o Tighten the remaining bolts (4) to 25 N•m (18 lb ft).



Pic 5
12. Install the fuel tank shield (1).
13. Install the fuel tank shield mount bolt (2).
14. Install the fuel tank shield mount nut (3).
Tighten
o Tighten the fuel tank shield mount bolt to 25 N•m (18 lb ft).
o Tighten the fuel tank shield mount nut to 12 N•m (106 lb in).
15. Install the rear wheel and tire assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
16. Lower the vehicle.
17. Refill the fuel system.
18. Install the fuel filler cap.
19. Connect the negative battery cable.
20. Perform the following procedure in order to inspect for leaks:
A. Turn the ignition switch ON for 2 seconds.
B. Turn the ignition switch OFF for 10 seconds.
C. Turn the ignition switch ON.
D. Inspect for fuel leaks.
21. Program the transmitters. Refer to Transmitter Programming in Keyless Entry.
 
Installation Procedure (Left)

Pic 6
1. Install fuel pump strainer in the same position as noted during disassembly. Push on the outer edge of the strainer ferrule until the strainer is fully seated.
2. Install a sender gasket on the fuel sender.
3. Insert the fuel sender through the fuel tank opening.
4. The fuel sender may need to be rotated in order to facilitate the installation.
Important
Do not bend or twist the float arm.
5. Insert the float and the float arm into the fuel tank opening.
6. Install the float arm retaining clip.

See Pic 2
7. Align the fuel sender gasket tab (1) with the fuel sender cover mark (2).
8. Align the fuel sender cover mark (2) with the fuel tank mark.
9. Tighten the fuel sender attaching bolts until the bolts are finger tight.

See Pic 2
10. Tighten the fuel sender assembly attaching bolts in proper sequence.
Tighten
Tighten bolts to 7 N•m (62 lb in).


11. Connect the fuel sender fuel feed pipe (1) from the jet pump to the left tank, to the fuel return rear pipe (2), and to the fuel feed rear pipe (3). Refer to Quick Connect Fitting(s) Service (Plastic Collar) .
12. Connect the fuel sender electrical connector.
See Pic 4

13. Install the fuel tank strap (3).
14. Install the fuel tank strap bolts (1, 2, 4).
Tighten
o Tighten the bolt (2) to 25 N•m (18 lb ft).
o Tighten the bolt (1) to 25 N•m (18 lb ft).
o Tighten the remaining bolts (4) to 25 N•m (18 lb ft).
See Pic 5

Install the fuel tank shield (1).
15. Install the fuel tank shield mount bolt (2).
16. Install the fuel tank shield mount nut (3).
Tighten
o Tighten the fuel tank shield mount bolt to 25 N•m (18 lb ft).
o Tighten the fuel tank shield mount nut to 12 N•m (106 lb in).
17. Install the rear wheel and tire assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
18. Lower the vehicle.
19. Refill the fuel system.
20. Install the fuel filler cap.
21. Connect the negative battery cable.
22. Perform the following procedure in order to inspect for leaks:
A. Turn the ignition switch ON for 2 seconds.
B. Turn the ignition switch OFF for 10 seconds.
C. Turn the ignition switch ON.
D. Inspect for fuel leaks.
23. Program the transmitters. Refer to Transmitter Programming in Keyless Entry.
________________________________________
Document ID# 776239
2002 Chevrolet Corvette

 

Thanks to Z06ster and DEEGEE. I appreciate the time you took to explain the problem and solution. It appears I could have purchased a 55 gallon drum of techron without making any difference.

 

Does sound like you might need to have the sending units replaced. Good luck with that repair.