Gas Gauge not working
 

Hello,

I have a 2004 Ford Sport Trac XLT. Replaced fuel pump, sending unit and had cluster rebuilt. Gas gauge still not working. I fill the tank drive about 15 miles and gauge goes to empty.

Welcome to the site..

When the gauge drops, does it stay down for the count until the tank is filled again?

The gauge works by the PCM supplying a reference voltage to the tank unit and a fuel level is sent back to the slosh Module as a signal return in an ohms value. Basically a varied ground. (Could ground the BK/OG and the gauge should peg Full)
Being the cluster was replace would/should take the Slosh Module off the table as a drop out to the gauge.

Excluding the cluster and tank connectors, there are a few other connectors inline for both PCM ref., and the sender to slosh for a sig. return.

There's two midship,, left side frame rail area about were the driver sits..
From those connectors you can measure resistance through the tank sender (Low fuel-22.5 ohms, Full-145 ohms) so if the gauge is reading Empty and the ohm value reads high through the connector when tested then the issue is forward of that connector or the PCM ref is missing. Same with the PCM Reference value into/for the tank unit. Checked/back probed at the connector the ref voltage for the gauge should be active there. If not, then the issue is forward within another connector or possibly PCM..

If your up for some testing, I can provide some check points...

Gas Gauge
 

Hello,

Here is what usually happens. I fill the truck and the gauge goes to full. I drive for about 15-20 miles and it quickly goes to empty and beeps and the low fuel light comes on. I drive, shut the truck off when I am done. If I start it it will go back up to full and sometimes go to 3/4 full. Drive some more and it goes to E again. As I stated, cluster was rebuilt and fuel pump sending unit replaced. I do not know anything about fixing autos so I would rely info to a friend of mine.
Thanks so much for your help.
-D