Mercury mountaineer fuel gauge

being honest you have me bt I have ha a simlar problen and it was the instrument cluster went and got a used one it worked fine and cheaper

Likely need a new level in the tank. There is a float in there that may be stuck or corroded to the point that the signal isn't getting g to the gauge. It's also possible the gauge in the dash is bad. I would go with the level sensor in the tank first.

REMOVE THE WHOLE PACKAGE AND SWITCH IGNITION ON AND TRY TO FIX CONNECTION AND CHECK IT OUT. MOVE FLOATER AND SEE WHAT YOU GET

depending on your year, make and model. most are located in the fuel tank with the electric fuel pump.

Fuel gauges are not meant to be precision instruments. You might want to fill up a 2 gallon can and drive the car until it runs out of fuel to see how low the gauge will go before it's really empty. Use the 2 gallons to get back to a filling station.
I once spent three working days trying to get a 1972 Chrysler to read full when it's full, half when it's half and quarter tank when the tank has a quarter amount of fuel. The customer did not want to accept anything else, but in the end all I did was to get close, not exact.
It is possible that the fuel float in the gas tank is "drowned", that is, the plastic float might have a slow leak and some fuel found its way inside. This will cause the float to submerge slightly and give you a low reading. To check this you will have to remove the float unit from the tank.
In any case, if you feel up the job (not easy) remove the float unit from the tank and manually move it up and down while checking the meter reading. You can bend the wire holding the float to correct misreadings.
Personally, I wouldn't bother, just be aware that when the reading is low, feel safe that you still have enough fuel to get to the next filling station.

there is two things : fuel gauge and dash fuel gauge. The fuel gauge in tank rated to 0 to 90ohms.disconnect wire at the tank take a variable resistor connect it to wire .read the dash gauge if it move as you move the resistor. if ok fuel tank gauge is at fault

The most common way to find out is to test both components.
The sending unit in most vehicles grounds the gauge on the dash.
You would unplug the sending unit - pump harness at the tank and ground the sending unit wire. If the gauge climbs up to full the sending unit is at fault.
You could also measure resistance in the circuit in the tank when the tank is close to empty and after filling it up. The resistance should be different each time.

If all voltages checked ok,then most probably its faulty instrument cluster board on which gauges are connected.Yes if cluster circuit board looks ok,then also it can be faulty.Somewhere there is minute short or burn on board then such prolem arises.
Also check the fuse box.One under hood and other under dash.Inspect each and every fuse and see if all are fine or not.
---------------For more troubleshooting on these cluster gauges i suggest you to refer the list of help links mentioned below.Its step by step instructions will help you to confirm the exact cause of problem in these conditions:---------
Click the link below:------

2004 Toyota Tundra: Oil Gauge and Temp Gauge Not Working?

http://howtobyme.blogspot.in/2012/05/2004-toyota-tundra-oil-gauge-and-temp.html

--------------

2005 Lexus SC430: Fuel Door, Dome light and Fuel Gauge Fuse Location?

http://howtobyme.blogspot.in/2012/05/2005-lexus-sc430-fuel-door-will-not.html
----------

Toyota 4Runner: Temperature Gauge Sensor

http://technoanswers.blogspot.in/2012/04/toyota-4runner-temperature-gauge-sensor.html
------------

Temperature gauge sits over half way mark?

http://schematicsdiagram.blogspot.in/2012/04/temperature-gauge-sits-over-half-way.html

---------------

Heater blows intermittently and temp gauge goes erratic?

http://technoanswers.blogspot.com/2012/01/heater-blows-intermittently-and-temp.html

----------

Temperature gauge does not move and no heat when heater is ON?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-does-not-move-and-no.html

-----------

2003 Pontiac Grand Prix: Erratic Fuel Gauge?

http://technoanswers.blogspot.in/2012/06/2003-pontiac-grand-prix-erratic-fuel.html

-----------

Temperature gauge keeps fluctuating up and down close to red?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-keeps-fluctuating-up.html

-------------

Temperature gauge on the dash quit working on Pontiac Grand Prix?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-on-dash-quit-working.html

---------------

Fuel gauge jumps from empty to full?

http://schematicsdiagram.blogspot.com/2011/12/fuel-gauge-jumps-from-empty-to-full.html

--------------

Gas gauge stuck on empty on 2002 Mercedes Benz 240c?

http://repairhelpcenter.blogspot.in/2012/02/gas-gauge-stuck-on-empty-on-2002.html
---------------

• Oldsmobile Temperature Gauge Lamp Switch?

-----------------

Fuel gauge drops to Empty?

http://technoanswers.blogspot.com/2012/01/fuel-gauge-drops-to-empty.html

----------------

Dodge neon gauges not working?

http://technoanswers.blogspot.in/2012/02/dodge-neon-gauges-not-working.html

------------

Temperature gauge went up?

http://schematicsdiagram.blogspot.com/2011/12/temperature-gauge-went-up.html

------------

Temperature gauge stays At cold on jaguar?

http://technoanswers.blogspot.in/2012/02/temperature-gauge-stays-at-cold-on.html
-----------

How to replace Instrument panel and dashboard on Toyota car?

http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-instrument-panel-and.html

-----------

How to remove instrument panel on Chevrolet car?

http://technoanswers.blogspot.in/2012/02/how-to-remove-instrument-panel-on.html

-----------

How to remove control panel on Buick regal?

http://howtobyme.blogspot.in/2012/02/how-to-remove-control-panel-on-buick.html
---------------
These details will help.Thanks.

If all voltages checked ok, then most probably its faulty instrument cluster board on which gauges are connected. Yes if cluster circuit board looks ok, then also it can be faulty. Somewhere there is minute short or burn on board then such problem arises.

Also check the fuse box. One under hood and other under dash.

Inspect each and every fuse and see if all are fine or not.

---------------

For more troubleshooting on these cluster gauges I suggest you to refer the list of help links mentioned below. Its step by step instructions will help you to confirm the exact cause of problem in these conditions: ---------

Click the link below: ------

2004 Toyota Tundra: Oil Gauge and Temp Gauge Not Working?

http://howtobyme.blogspot.in/2012/05/2004-toyota-tundra-oil-gauge-and-temp.html

--------------

2005 Lexus SC430: Fuel Door, Dome light and Fuel Gauge Fuse Location?

http://howtobyme.blogspot.in/2012/05/2005-lexus-sc430-fuel-door-will-not.html

----------

Toyota 4Runner: Temperature Gauge Sensor

http://technoanswers.blogspot.in/2012/04/toyota-4runner-temperature-gauge-sensor.html

------------

Temperature gauge sits over half way mark?

http://schematicsdiagram.blogspot.in/2012/04/temperature-gauge-sits-over-half-way.html

---------------

Heater blows intermittently and temp gauge goes erratic?

http://technoanswers.blogspot.com/2012/01/heater-blows-intermittently-and-temp.html

----------

Temperature gauge does not move and no heat when heater is ON?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-does-not-move-and-no.html

-----------

2003 Pontiac Grand Prix: Erratic Fuel Gauge?

http://technoanswers.blogspot.in/2012/06/2003-pontiac-grand-prix-erratic-fuel.html

-----------

Temperature gauge keeps fluctuating up and down close to red?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-keeps-fluctuating-up.html

-------------

Temperature gauge on the dash quit working on Pontiac Grand Prix?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-on-dash-quit-working.html

---------------

Fuel gauge jumps from empty to full?

http://schematicsdiagram.blogspot.com/2011/12/fuel-gauge-jumps-from-empty-to-full.html

--------------

Gas gauge stuck on empty on 2002 Mercedes Benz 240c?

http://repairhelpcenter.blogspot.in/2012/02/gas-gauge-stuck-on-empty-on-2002.html

---------------

• Oldsmobile Temperature Gauge Lamp Switch?

-----------------

Fuel gauge drops to Empty?

http://technoanswers.blogspot.com/2012/01/fuel-gauge-drops-to-empty.html

----------------

Dodge neon gauges not working?

http://technoanswers.blogspot.in/2012/02/dodge-neon-gauges-not-working.html

------------

Temperature gauge went up?

http://schematicsdiagram.blogspot.com/2011/12/temperature-gauge-went-up.html

------------

Temperature gauge stays At cold on jaguar?

http://technoanswers.blogspot.in/2012/02/temperature-gauge-stays-at-cold-on.html

-----------

How to replace Instrument panel and dashboard on Toyota car?

http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-instrument-panel-and.html

-----------

How to remove instrument panel on Chevrolet car?

http://technoanswers.blogspot.in/2012/02/how-to-remove-instrument-panel-on.html

-----------

How to remove control panel on Buick regal?

http://howtobyme.blogspot.in/2012/02/how-to-remove-control-panel-on-buick.html

---------------

These details will help.

Thanks.

your float is stuck on the fuel pump