Fuel gauge gone crazy

[FiremanBob]

My 2001 Ranger, 2.3L Duratec/manual crossed 295K miles a month ago. But starting last summer the fuel gauge started reading very high, even pinning at the top of the scale, way above full, after a fillup. It gives inconsistent readings - sometimes nearly accurate, sometimes high. I put in a new fuel pump about 10K miles ago - a premium one from NAPA and it read fine until it suddenly it didn't. Is this likely to be in the fuel pump, or an electrical issue?

 

[RonD]

Welcome to TRS

Maybe, but if it was reading oddly before the new pump/sender was put in then more likely to be the Anti-slosh module on the back of the instrument cluster

The sender/float setup in the gas tank uses these parameters
16 ohms EMPTY
158 ohms FULL

Sender is grounded, by one wire(black), and then there is a Yellow wire that runs to the back of the cluster
That yellow wire is the "ground" for the gas gauge, well the resistance to ground

But on the back of the cluster is a separate module, it unplugs, that is used to prevent the gas gauge needle from swinging up and down every time you go around a corner and the gas in the tank sloshes around, the Anti-slosh module, it delays direct reading of the "ground" so sends an average ground to the gauge
It can fail
Usually you get Empty or Full all the time but it can fail in different ways

You can use a OHM meter on the top of gas tank to test sender, should read between 16 and 158 ohms, rock the truck to get gas sloshing around and you should see OHMs changing accordingly, but not jumping around wildly, that would be a bad sender

Or you can pull out the cluster and test the yellow wire at that end, same test
And change the module if OHMs look OK

 

[FiremanBob]

Thanks. The gauge ran fine for about a year after I installed the new fuel pump.