I have a 2002 lincoln ls that has gas guage reading only a quarter tank when full. I know there is 2 pumps on this car, one is the primary pump under passenger back seat and a jet transfer pump on drivers side under backseat. Both have floats with switches so which one actually sends the fuel level to the gas guage???

most cars have a pump some place near the gas tank if not inside near the gas pickup but that requires dropping the tank from the car if not follow the leads around where the fuel line is and the pump should be there on the side wall of the car in most cases

Does not have fuel pump driver module , has rear electronic module ! The difference is it does more then just fuel pump control . I would google it to see what it looks like , then look in the trunk ,under back seat , Have seen them behind back quarter trim panels .

Does the pump have wick disconnects that required a tool to remove them? There are orings in those as well as a large oring sealing the pump to the tank. Make sure the connectors click when you replace them. The pump should activate with the key on. " not started", you should be able to see if the lines are leaking or if it just your fuel fill overflow hose leading to the fill door alongside the large full hose.

could be your fuse,watch this video first. Lincoln LS Fuel Pump Here's a second video showing you how to remove fuel pump if that is what is wrong,but check the fuse first. Removing Fuel Pump from 2000 Lincoln LS V8 I have a lincoln LS with the 3.0 engine,luckily my fuel pump hasn't did me wrong,I better go knock on wood.But I do need a new radiator.

2002 Lincoln LS uses a saddle-type fuel tank consisting of 2 fuel pump modules. A fuel transfer pump in the left side of the fuel tank supplies fuel to the right half, which contains The Fuel Pump Module (FPM). The FPM contains the fuel level sensor and an inlet filter. The FPM is controlled by the Fuel Pump Driver Module (FPDM) which is integrated into the Rear Electronic Module (REM) Fuel pressure is regulated by a pulse-width modulator in the FPDM which cycles the fuel pump on and off at varying intervals depending on engine load and RPM. The FPM supplies fuel under pressure to the fuel injection system supply manifold and a fuel level signal to the fuel gauge on the instrument panel.
It is recommended that if one of the fuel pumps fail that BOTH pumps be replaced as a set to avoid repeat repairs. (If one pump has been running for 1500 hours and the motor is worn out, the other pump also has been running for 1500 hours and is very likely to fail shortly thereafter.)

most likely it is the sending unit located in the gas tank you need to remove the gas tank it is a complete assy including fuel pump

The gas tank sounds like a bad ground usually located under the car at the gas tank. I do not know but maybe they both tach and fuel gague get their ground from the same place.

There are two pumps. One is a transfer pump.
The pumps are in the plastic fuel tank under the car,under the rear seat area.
Have to remove drive shaft,then tank, to get to the pumps.

Fuel pump and the sensor that detects the gas level are both inside the gas tank.

The gas guage has a sending unit in the tank attached to the pump, there is a small circuit board on it that has smal"fingers" that send the signal to the guage.These get worn off and thus sends a false reading to the gas guage in the dash. The gas tank must be removed and a new unit put in to solve the problem. I had to do this repair to mine. As for the gas issue, just try pulling the nozzle back out of the filler neck when putting gas in, sometimes the overflow tube gets plugged up and won't allow the air to escape as the gas goes in the tank, making the gas pump think the car is full, pulling the nozzle will allow the air to escape. Hope this helps.