My fuel gauge shows me that i have a full tank after driveing a couple hundred miles or it seems to tell me how much i have but i feel that i actually have less gas than what it tells me. it gives me inaccurate readings. i have tried reseting the computer and it still has not fixed the problem.

Fuel sender is typically integrated with the in-tank fuel pump. These do age with many cycles. Try a reasonably good quality fuel injector cleaner for a couple tanks of gas- your injectors probably would benefit and it sometimes fixes the problem. If not, pumps and sender combinations are over a hundred bucks and at least that much labor to replace. What model/year vehicle? How To Diagnose Fuel Gauge Easy Not in the Book Tricks

with out further info I would guess sending unit on fuel gauge is bad,that would be located in fuel tank

replace front fuel pump because gauge is made into fuel pump and not serviceable. Or poor boy way of getting by would be fill front tank with gas reset mileage drive normal for a day. refill again with gas note gallons used and mileage driven for average miles per gallon. front tank should be around 17 gallons multiply by mile per gallon you figured

Sounds like your sending unit could be bad.

Normal. There is a resister in the fuel level circuit that slows down fuel level readings. A gauge that responded instantly to a sloshing fuel level every time you went over a bump or around a turn would drive you crazy.

It sounds like the wiring harness that the fuel pump assembly plugs into. Check to see it there is a replacement one available.

the gas is regulated from the switching valve you control off the dash. Check the valve to hear it switch
have a friend help you do this. it will be located under the truck between the two tanks. You may have a faultly valve or switch rattling inside changing the tanks setting also while driving which will be hard to tell

The fuel level sensor is bad. The tank will have to be taken down to replace the level sensor. There is little fingers on the resistor that wear down and loose contact causing the gage to read incorrectly.

the buffer plates in the tank seem to be loosely held! so sometimes they fall on the sender unit,causing the gauge to drop!!!!! when the vehicle is shaken!!!! remove that tank and have the plates checked!!!!

that's...thirty liters or so?...10.4 liters per hundred. I'm getting 30 UK MPG...that sounds rather low for a 1.2 . it should be getting 35-40, I believe. better get yourself a tuneup if you can afford it.