Fuel gauge shows above full.
I got my '99 F150 used, years ago. Ever since I have owned it the fuel gauge, when tank is full as shown above, also still shows about 1/8 to 1/4 of a tank when the tank is bone dry.
I've been told this is likely because of the float in the fuel pump which I'm guessing was previously replaced. Otherwise, is there a good fix or adjustment for this?

 

Use the dash diagnostics to see if the gauge reading corresponds to the digital level value. Below is copied and pasted from some of Bluegrass's posts:

To trigger the dash HEC diagnostics.
Press and hold the speedo reset 'in' , turn ignition to 'run', then start the engine, then release the reset button.
Step to the word 'fuel' and read out what the display says. It should read the present level in the tank as determined by the solidstate logic.
This readout will be an 'octal' number between 0 and 255.
Values:
0-18 = a short ckt.
41 = E mark.
54 = low fuel and light.
93 = 1/4.
138 = 1/2.
178 = 3/4.
215 = full mark.
232 = full stop.
255 = open sender ckt.

Reference thread:

https://www.f150online.com/forums/19...-problems.html

 

It also flickered to 255.
so I guess that's telling me that the tank is full, which I already knew... But the gauge is show "beyond full" and it goes down to a little above the 1/8 tank mark when I run out of fuel.
So I'm back where I started. How do I fix this?

 

So maybe the float for the fuel gauge is not sitting correctly of hung up on something?

Have you tried maybe driving down a gravel road with pot holes and let the truck go through those pot holes and jar the truck around a bit to see if the float will break free?

Or... with the fuel tank at different levels of fullness, drive 5 miles an hour or so and then come to an abrupt Stop, let the fuel slosh around in the tank real good for 30 seconds, do this several times... ?

(just some old school thinking going on from me here...lol)

 

Run it down to 3/4, 1/2, and 1/4 and see what the readout is.

Note that it should NOT read 255, even momentarily.

 

Don't know if you can see the digital readout, but it shows fuel level at 84 which is right, and shoul be just under 1/4 tank... But the gauge/needle still shows above 1/4 tank. So it seems the fuel tank float is ok, but the gauge on itself is off.... So how do I fix that?

 

I don't know how to fix that, but it looks like your gear pointer is out of adjustment. Here is how you fix this:

https://www.f150online.com/forums/ar...inter-fix.html

 

Thanks! What a great and simple fix! I'll do it this weekend. Daughter drove my truck and someone hit her, passenger front fender two years ago. It jumped position then. I just assumed it was a major hassle, linkage fix or something.

 

Linkage should be okay if it starts in Park and Neutral and shifts into the proper gear when you move the lever. When under the dash, make sure the 2 Torx screws holding the shift tube are not loose. If they are loose, the lever will feel sloppy.

 

Fuel level sender;
140 Ohms +/- a small amount Full tank.
20 Ohms +/- a small amount for empty.
If both are ok, dash panel is in fault.
Measure either at tank or the dash panel 16 lead connector pulled off.
Measure between #5 pk/or and #10 yel/wht leads.
Be sure there is no power on either lead, first.