Fuel gauge won't display level, fuse is good

Yeah, quit trying to play auto mechanic an take it to a qualified repair shop. You have no clue how it works.

Fuel Gage Inaccurate or Inoperative (Buick)

Turn the ignition switch to the RUN position.
Using a scan tool, inspect for Powertrain Control Module (PCM) diagnostic trouble codes (DTCs). Refer to Engine Controls in order to diagnose PCM DTCs.
Turn the ignition switch to the OFF position.
Disconnect the fuel tank unit connector.
Connect the 2 red leads from the J 33431-C to the harness connector terminal B and terminal D.
Turn the ignition switch to the RUN position.
Set the tester resistance dials to 40 ohms (EMPTY).
Set the tester resistance dials to 248 ohms (FULL).
Does the fuel gauge display E at 40 ohms and F at 248 ohms?


Fuel Gauge (Buick, Pontiac)
The magnetic fields of the 2 coils move the fuel gauge pointer. The coils are at right angles to each other. The 2 coils are connected to each other. The fuel level Pulse-Width Modulated (PWM) circuit from the PCM connects at a middle point. Battery voltage is applied to the end of the coil at the E end. Ground is applied at the other coil's F end.
The fuel level sender resistance is proportional to the fuel level. The voltage across the sender is the fuel level input signal that is applied to the PCM on CKT 30 and CKT 452. The PCM provides a Pulse-Width Modulated (PWM) fuel level output signal on CKT 455 (PPL/WHT) to the instrument cluster fuel gauge.
When the tank is low, the fuel level sender resistance is low. A larger current passes through the E coil in order to move the pointer toward E on the scale. When the tank is full, the sender resistance is high. More current flows through the F coil. This moves the pointer toward F on the scale.
With 2 coils operating the pointer, the gauge is not affected by changes in the vehicle's electrical system.

That won't affect the fuel gauge. Different circuits, entirely. Any issue with the fuel gauge is between the gauge on the dash, a little wiring to the gas tank, and the sender unit inside the tank. In most cases, the problem turns out to be the sending unit inside the tank.

To check the gauge itself for working, you can ground the fuel gauge wire at the gas tank connector, and watch for movement on the gauge, with the key in ON. You take the connector off at the gas tank, find the wire for the fuel level sender (or gauge), and touch it to a good ground- a metal piece on the car frame. If gauge is good, the needle will move either to full or to empty, but you can see the needle move to a new point, when you (temporarily, only temporarily) ground the fuel gauge wire. The key in the switch must be in on. If this causes the needle to move, then the dash gauge is good, and the problem is the sender unit in the tank. This unit has a variable resistor, not too expensive. The fun is getting to it.

It is in the instrument cluster, which has to be removed to replace the gauge. It cannot be repaired. Did you first check the 10 amp METER fuse in the fuse panel?

Now let me say, that when the gauge quits, it is more often a fault in the sending unit in the gas tank, and not the gauge. Here is how to find out if your gauge is good: Find the fuel tank electrical connector, and pull it apart. You will need a small jumper wire. Find the blue wire in the body side of the connector (not the fuel tank side). Put the jumper wire into the blue wire terminal, turn the ignition key to on not start, and ground the jumper wire to a metal frame piece. Someone needs to watch the fuel gauge needle while the wire is grounded. If the gauge in the dash is good, the needle will move. It will probably go to either full or empty, but if the needle moves, the gauge is good and the fault is in the sending unit in the tank. Don't give up testing until you are sure the jumper wire is being grounded good to the frame. Just touch the wire to frame and watch the needle movement, once sure, stop so you don't blow the fuse. If the needle doesn't move, first check the 10 amp meter fuse. If fuse is good, it must be the gauge.

make sure the sender is grounded or your guage wont work at all..there should be a ground wire .. if not add one someplace..

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.
   

Hello
The porblem under discussion here is not related with my expertise. Please get helped from any other. OK.

Most of the time it's the fuel level sender in the tank that is the problem. The sender wears a bit as the fuel level float moves up & down and the result is a gauge that may read properly in a couple of spots but may show that the tank is empty or full at other times no matter how much fuel is in the tank. A few of these senders are replaceable but many only come as a part of the fuel pump module. Generally if the sender is bad and the vehicle has close to 100k miles on it I suggest replacment of the pump at the same time even if the sender is sold by itself. I've found that OEM parts work best on these as you don't wan't to have to do this job twice. Good luck and hope this helps!

Not a fuse.There is no fuse for the level sensor.These are known for fuel level sensors being bad.Sometimes they will leave a code and sometimes not.You can check codes and see if you have a fuel level sensor code.The other thing you can do is check the connections and make sure they are clean and on securely.If you find that the level sensor is bad.Then it is easier to replace if the fuel in the tank is as low as possible for easier removal of the fuel tank.Hope this helps.Good luck.

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 fuel level sensor inside your gas tank might be defective
you need to drop the tank and check the level sensor