Hello & Welcome,
Can you tell us how the gauge is behaving?
Hi again & thanks for that information.
Probably 95 percent of the time, the problem is the fuel level sender itself. I have a 2001 GM vehicle that had the same problem just last year. The fuel additive is a good idea, but what usually happens (like in my vehicle) is that the little metal "fingers" on the fuel sender get weak, bend, and break. There are 3 fingers on the sender so when one of them breaks it makes a good connection every now and then and will appear to work, then it goes bad again as the sender moves.
There are some tests that can be done to verify the rest of the system, but you will most likely find that the sender is bad and needs to be replaced. You may be able to replace the level sender separately from the fuel pump assembly, but it wouldn't be a bad idea to just replace the whole thing at one time. It will most likely involve dropping the fuel tank to replace it.
I hope this helps. Please let me know what you decide to do.
Take Care, Greg A.
Hi again - sorry for the delay.
Let me check the procedure and see what it says.
Back soon, Greg A.
Here is the procedure, which look pretty straight forward. You might want to print this out and read it over a couple of times before you being.
Fuel Vapors can collect while servicing fuel system parts in enclosed areas such as a trunk. To reduce the risk of fire and increased exposure to vapors:
In order to prevent damage, cover the fuel pipe fittings with a shop towel before disconnecting the fuel pipes or removal of the fuel sender retaining ring, in order to catch any fuel that may leak out. Place the towel in an approved container when procedure is completed.
The modular fuel sender assembly will spring-up when the locking ring is removed.
Do Not handle the fuel sender assembly by the fuel pipes. The amount of leverage generated by handling the fuel pipes could damage the joints.
When removing the fuel sender assembly from the fuel tank, the reservoir bucket on the fuel sender is full of fuel. The fuel sender must be tipped slightly during removal in order to avoid damage to the float. Place any remaining fuel into an approved container once the fuel sender is removed from the fuel tank.
Care should be taken not to fold over or twist the fuel pump strainer when installing the fuel sender assembly, as this will restrict fuel flow. Also, assure that the fuel pump strainer does not block full travel of the float arm.
Always replace the fuel sender seal when reinstalling the fuel sender.
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten the fuel sender access panel bolts to 2 N·m (18 lb in).
I did check and it says that you can replace the sensor separate from the fuel pump, but the choice is yours on that.
Please let me know how it goes.