Just thought i'd post this to possibly save someone out there a boat load of money like I did.
I almost went to the dealer and purchased a new fuel sending unit but decided to try something just for kicks, and boy am I glad I did.
First off, I posted a few days ago stating that I ran my truck out of fuel with the gauge showing 1/4 of a tank of fuel.
The sending unit had failed.
Today I dropped the tank, and just before running out and giving the stealership almost 500 bucks, I grabbed my can of "Mass Air Flow Sensor Cleaner" spray.
It is a high pressure spray can, similar to carb cleaner but I imagine, not NEARLY as harsh.
I sprayed tons of the stuff in and around the plastic sending unit sensor area where the fuel float up and down "action" takes place. (like the pivot point, where the sensor ITSELF is located)
I let the stuff dry fully, and started running some tests positioning the float wire in different positions and cycling the ignition, including at very low levels where the fuel light is ON, where it would not correctly indicate before.
Just wanted to toss this in here... (better late than never)
My sending unit had corrosion and rust on it an ultimately failed.
The same thing happened with my 78 f-350 after purchasing it not running with 5 gal of water! in the fuel tank. (looked like a cavern of rust icicles up to 5" long in the tank) Well after replacing the entire fuel system (lines, tank, pump, carb) I found that the dump body i had, used a custom side mount tank. Nobody made a replacement sending unit. What to do?... Well, I pulled it disassembled it to expose all of the contacts and ran it through my sand blaster. Soaked it in wd-40 bent any loose contacts back to grip better, put it back in and now 2014 still works like a charm.
Same thing happened to my 02 F-550 Read 1/4 when empty and empty when full. Pulled it out sand blasted the inside, reassembled and works like a charm again. Transfer Flow discontinued the part for my tank and oem one (if i could get it to fit) would have been over $400.
So save yourself the money and give it a shot If you don't have a blaster toss a guy $40 to hit it for you. Well worth it. Also keep it lubed by adding Marvel mystery oil or ATF once in a while to the tank if your running a gas engine. ( I usually do this once a year in the summer)