Fuel Gauge Malfunction

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97 Avalon, gauge reads incorrectly (shows full as 3/4) below 3/4 of a tank, gauge is accurate. I tried using a few fuel system cleaners, but they were no help. Could it be the sending unit?
 
My Buicks fuel gauge started acting up and I changed the entire fuel pump (which included a new 'sending unit'). It now works perfect. The price difference between a sending unit and a new, aftermarket (Spectre brand) fuel pump wasn't that much (at Rock Auto). I figured with 110K the OE pump might also be tired.
 
Have you tried cleaning the electrical terminals (or wiring harness connectors)? Could be nothing more than corrosion on important electrical connections associated with sending unit or gauge. Wouldn't hurt to clean them on a 13 y/o car.
 
Originally Posted By: parimento1
97 Avalon, gauge reads incorrectly (shows full as 3/4) below 3/4 of a tank, gauge is accurate. I tried using a few fuel system cleaners, but they were no help. Could it be the sending unit?



The only fuel system cleaner able to help "fix" erratic fuel sender s is TECHRON. It will remove the sulphur (from cheap gas usually) from the contacts.
 
Techron type products or MMO often help.
But fuel sending units are hardly changed from the 1930s except that cork is not used as a float anymore.
They do go out, here and there.
 
Originally Posted By: parimento1
I would have to go into the tank to clean terminals huh


Wouldn't the sending unit terminal/s be on the outside of the tank?
 
Originally Posted By: Rumble
Originally Posted By: parimento1
I would have to go into the tank to clean terminals huh


Wouldn't the sending unit terminal/s be on the outside of the tank?


Yes there are terminals there - but the contacts that wear or get dirty and effect gauge readings are in the tank submerged in gasoline.

GM actually has a TSB for the use of TECHRON for this issue before replacement. It was a big issue on C5 Corvettes.
 
I tried two bottles of Techron previously, no change. I ordered the fuel sending unit today and will install it soon. I looked at the Haynes manual and it looks very straightforward. Anything I should know before doing this?
 
mine was acting crazy----i would fill up and it would go up slightly then go "empty" I added seafoam to the tank several times and I appeared to help a lot.
 
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