Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Fuel Mixture Heating System

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See Figures 1 and 2



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Fig. Fig. 1: Fuel mixture heater-carbureted engine shown, E16i engine similar



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Fig. Fig. 2: Typical fuel mixture system-1986 E16S engine shown, others similar

The system's purpose is to promote better atomization of the fuel during cold engine operation. The system uses an electric grid style heater under the carburetor or throttle body, to heat the air/fuel mixture when the engine is below normal operating temperature.

When the engine starts, the heater energizes and the air/fuel mixture is heated as it passes through the heater grid. When engine warm-up is complete, the current is cut off by the ECU or mixture heater relay.

TESTING & INSPECTION



System Inspection

This test must be performed with the engine below 122°F (50°C).

  1. Disconnect the electrical connector from the mixture heater.
  2.  
  3. Connect a voltmeter across the terminals of the mixture heater electrical connector.
  4.  
  5. Turn the ignition switch to the ON position, but do NOT start the engine. Observe the reading on the voltmeter.

    If the reading is approximately battery voltage, proceed to the next step.
     
    If the reading is not approximately battery voltage, inspect the mixture heater relay, choke relay, water temperature switch and power supply circuitry for a fault.
     

  6.  
  7. Connect an ohmmeter across the mixture heater terminals. Check the continuity between the heater terminals. If continuity does not exist (open), replace the carburetor insulator assembly.
  8.  

Mixture Relay Testing

See Figures 3 and 4



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Fig. Fig. 3: Fuel mixture heater relay terminal identification-Sentra



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Fig. Fig. 4: Fuel mixture heater relay terminal identification-Pulsar

  1. Remove the relay from the vehicle.
  2.  
  3. Connect an ohmmeter across terminals 3 and 4 . Continuity should not exist.
  4.  
  5. Connect a 12 volt battery source across terminals 1 and 2 . Continuity should now exist across the terminals.
  6.  
  7. If the relay did not perform as specified, replace the relay and recheck system operation.
  8.  

 
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