Aspen 2007, Durango 2005-2007

Fuel Level Sending Unit/Fuel Pump Module

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Description & Operation



The fuel gauge sending unit (fuel level sensor) is attached to the side of the fuel pump module. The sending unit consists of a float, an arm, and a variable resistor track (card).

The fuel pump module has 4 different circuits (wires). Two of these circuits are used for the fuel gauge sending unit for fuel gauge operation, and for certain OBD II emission requirements. The other 2 wires are used for electric fuel pump operation.

For Fuel Gauge Operation: A constant input voltage source of about 12 volts (battery voltage) is supplied to the resistor track on the fuel gauge sending unit. This is fed directly from the Powertrain Control Module (PCM).


NOTE
For diagnostic purposes, this 12V power source can only be verified with the circuit opened (fuel pump module electrical connector unplugged). With the connectors plugged, output voltages will vary from about 0.6 volts at FULL, to about 8.6 volts at EMPTY (about 8.6 volts at EMPTY for Jeep models, and about 7.0 volts at EMPTY for Dodge Truck models).

The resistor track is used to vary the voltage (resistance) depending on fuel tank float level. As fuel level increases, the float and arm move up, which decreases voltage. As fuel level decreases, the float and arm move down, which increases voltage. The varied voltage signal is returned back to the PCM through the sensor return circuit.

Both of the electrical circuits between the fuel gauge sending unit and the PCM are hard-wired (not multi-plexed). After the voltage signal is sent from the resistor track, and back to the PCM, the PCM will interpret the resistance (voltage) data and send a message across the multiplex bus circuits to the instrument panel cluster. Here it is translated into the appropriate fuel gauge level reading.

For OBD II Emission Monitor Requirements: The PCM will monitor the voltage output sent from the resistor track on the sending unit to indicate fuel level. The purpose of this feature is to prevent the OBD II system from recording/setting false misfire and fuel system monitor diagnostic trouble codes. The feature is activated if the fuel level in the tank is less than approximately 15 percent of its rated capacity. If equipped with a Leak Detection Pump (EVAP system monitor), this feature will also be activated if the fuel level in the tank is more than approximately 85 percent of its rated capacity.

Removal & Installation



  1. Remove fuel tank.
  2.  
  3. Remove fuel pump module.
  4.  

  1. Install fuel pump module.
  2.  
  3. Install fuel tank.
  4.  

The fuel gauge sending unit (fuel level sensor) and float assembly is located on the side of fuel pump module. The fuel pump module is located inside of fuel tank.

2 Door Models
  1. Unplug 4way electrical connector.
  2.  
  3. Disconnect 2 sending unit wires at 4way connector. The locking collar of connector must be removed before wires can be released from connector. Note location of wires within 4-way connector.
  4.  
  5. The sending unit is retained to pump module with a small lock tab and notch. Carefully push lock tab to the side and away from notch while sliding sending unit downward on tracks for Removal & Installation. Note wire routing while removing unit from module.
  6.  

  1. Position sending unit into tracks. Note wire routing.
  2.  
  3. Push unit on tracks until lock tab snaps into notch.
  4.  
  5. Connect 2 sending unit wires into 4way connector and install locking collar.
  6.  
  7. Connect 4way electrical connector to module.

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  8.  

4 Door Models
  1. Remove electrical connector at sending unit terminals.
  2.  
  3. Press on release tab to remove sending unit from pump module.
  4.  

To Install:

The fuel gauge sending unit (fuel level sensor) and float assembly is located on the side of fuel pump module. The fuel pump module is located inside of fuel tank.

  1. Position sending unit to pump module and snap into place.
  2.  
  3. Connect electrical connector to terminals.
  4.  

 
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