Incorrect fuel reading tank shows empty, but can only pump 50 gal

What's the make of your truck

 

i have never known or driven any truck made to have accurate fuel gauges.

i would "stick" the tanks, and using a chart get a value of what the fuel levels were in each tank. after that, i'd not bother no more, and fuel up accordingly.

you could bring this up to the shop, they may be able to remove the sending unit (float) and make an adjustment, or they may replace them.

 

If it’s a Freightliner it is typical! I’ve had 2 freightliners and the fuel gauge does exactly what you describe from time to time.

 

Find someone with a texa computer you can change the fuel tanks buy plugging into the 9 pin

 

Both my trucks did the same thing, show the yellow/red near empty light on the gauge but only took 100 gallons to fill up (200 gallon capacity).

 

Most (all?) trucks only have one fuel level sensor. As long as both tanks stay level it doesn't matter.

What I've seen a lot of is shops don't ever replace with the correct sensor. They will put one for a 100 gallin tank in a 120 for example.

 

Yes I just reset my GPS mileage to zero when I fill up and I know the max distance I can go before MT.