My 2008 Mariner fuel gauge goes to full when i start it and back to empty when i turn it off, i have no mid range readings.

SOURCE: Fuel Gauge Promblem

Best to chk. all connections, sounds like a poor ground either buy the tank, or in the dash. It also could be a fulty sending unit or flote in the tank.

George Fischer

• 236 Answers
• Posted on Jun 19, 2009

SOURCE: mercury mountaineer fuel gauge

its either the sending unit or the gauge or the unit inside the gas tank

SOURCE: Fuel Gauge reads full all

sounds like it is not hooked up or not correctly. I would double check the connection on the fuel pump. Hope this helps tim

SOURCE: fuel gauge problem

Got the same problem, when empty fuel gauge shows full but fuel indicator light lights on.
Problem was the gauge itself and replaced by a second hand one.
How to remove: Remove the front glass (8 screws), remove the black frame (free), pull out both gauges (Fuel & Temp) they come togheter with their frame using a little screewdriver under their corners. Push the new unit in.That's it. Michel

SOURCE: I have a 1992 Mercury Grand Marquis Ls with a fuel gauge that does not work (gauge may be reversed)??? help please.

The fuel level indicating system is a magnetic type system, which consists of the sending unit located in the fuel tank, an anti-slosh module located on the back of the instrument cluster, and a fuel gauge located in the instrument cluster. The sending unit changes resistance according to the level of fuel in the fuel tank, which varies the current flow through the gauge.The pointer position varies proportionately to the current flow. In this system, the sending unit resistance is low (22 ohms) when the fuel level is low and high( 145 ohms) when the fuel level is high. The pointer of the magnetic gauge remains in position when the ignition is turned to the Off position. On some models, an anti-slosh module is used to dampen out fluctuating fuel signals from the sender. Some vehicles are equipped with a low fuel warning indicator. The anti-slosh module will also actuate the low fuel indicator when the fuel level in the tank reaches 1/16 to 1/8 full.


Do your other gauges/warning indicators work properly with the ignition on? If not, check for power at the fuse panel/fuses.

If they do then partially remove your cluster with connector still installed and check for voltage at cluster connector and gauge. Check continuity of cluster and gauge for ground.

Sometimes the anti-slosh module (if installed) goes bad in the Grand Marquis but not likely.

Sender troubleshooting:

1. Perform test with resistors as follows:

1. Disconnect wiring connector at sender unit, then connect resistor between gauge lead and a suitable ground.
2. Turn ignition switch to On position.
3. With 145 ohm resistor, the gauge pointer should contact the Full mark.
4. With 22 ohm resistor, the gauge pointer should contact the Empty mark.

1. Perform test with fuel sender of known quality as follows:

1. Turn ignition to Off position.
2. Disconnect wiring connector from sender and connect it to test sender.
3. Move float rod away from fuel filter against Full stop position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or above the Full mark.
4. Move float rod toward fuel filter against Empty stop position. Turn ignition switch to Off position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or below the Empty mark. If gauge works properly replace sender, which involves dropping fuel tank.