I just got a 2005 Freestar and the fuel gauge showed empty. I filled it up, took over 24 gallons, and the gauge still showed empty, with the low fuel warning light on.

For a few minutes, as I drove it home, the gauge moved up to about 1/8 of a tank, so the warning light went out. But then the needle went back to completely empty, and the warning light came back on.

How do I diagnose and fix this?

 

You may have "Sulfur Contamination" of your sending unit. Sulfur in the fuel coats the windings and causes the sending unit not to read the resistance of the windings causing the fuel gauge no to read or be erratic. I would try adding 2-20 oz. bottles of "Techron Concentrate Plus Fuel System Cleaner" to your tank and fill it up. Run the tank down to see if it clears. You may even need to try another double dose to clear it. My Son-In-Law had the same issue with his 2003 Explorer (no fuel reading) about a year ago. I told him to do the same. He added 2 bottles to a full tank and his issue cleared up after using about 3/4 of the treated tank. Has been fine since. He now adds one bottle every time he gets his oil changed. It's a lot cheaper to try than to spend $$$ that you don't need to.

 

I needed a new battery. After I got one, the fuel gauge slowly went up to full over about an hour of driving. Since then it has been fine.

The car sat for some time, with tank empty, before I bought it at auction. So it could be, the float was a little stuck. Or could be the weak battery. Or combination of both.

If I have any further problems I will try the Techron. Or maybe do it anyway, as a preventative measure.

 

If it was me, I'd do it anyways...Autozone is running a sale of 2 for $8...

 

As I said, it finally got off Empty and eventually got to Full, which it was. But I've driven about 100 miles since filling it, and the gauge is still past Full, hasn't budged.

Anyway, today I bought the 2 cans of Techron at the Autozone sale, and put them both in. Hopefully that will free up whatever might be sticking and the gauge will operate correctly. Time will tell.

 

Hopefully, the Techron will work for you. Ford wanted a ridiculous price to replace the fuel pump/sending unit in the Son-In-Laws Explorer. So for about 6 months, he was going by how many miles he was driving (and complaining about it being a PITA) before my Daughter called her favorite mechanic at DAD's Garage . Sulfur contamination was the 1st thing that popped in my mine along with the fix. Seen it several time on different makes and models.

 

I really thought this was solved. The gauge finally started going down as I drove more miles and used more fuel. Got down to between 1/4 and 1/2, then I filled up again and it took 17 gallons, so all seemed fine.

Started the car, and it reads Empty again, with warning light again

 

After about 20 miles of short trips, now it works again, goes to Full.

It seems that after a fillup, it gets "stuck on empty. For a time which got shorter after I added the Techron. So maybe it will clear up on its own. but to know that, after a fillup, it will read Empty for only a short time, I can live with that.

 

Stupid gremlins...Don't you just love them...