GM Firebird 1982-1992 Repair Guide

Early Fuel Evaporation (EFE)

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See Figures 1 and 2

OPERATION



The EFE system is used on some of the engines to provide a source of rapid engine heat up during cold operations. It helps reduce the time that carburetor choking is required and helps reduce exhaust emissions.

There are two types of EFE systems. The vacuum servo type, consists of a valve located in the exhaust manifold, an actuator and a Thermal Vacuum Switch (TVS). The electrical type, consists of a ceramic grid located under the base of the carburetor.

A check of the operation should be made at regular maintenance intervals.

TESTING



Vacuum Servo Type
  1. With the engine cold, observe the position of the actuator arm. Start the engine. The arm should move toward the diaphragm (closing the valve).
  2.  
  3. If the arm does not move, remove the hose and check for vacuum. If still no vacuum, remove the top hose from the TVS switch and check for vacuum.
  4.  
  5. If vacuum is present in the top hose, replace the TVS switch.
  6.  
  7. If vacuum is present at the actuator and it does not move, try to free the valve. If the valve cannot be freed, it must be replaced.
  8.  

Electrical Type

  1. Turn the ignition ON with the engine cold and probe both terminals of the heater switch connector with a test light.

    If 1 wire has power, replace the heater switch.
     
    If neither wire has power, repair the ignition circuit.
     
    If both wires have power, probe the pink wire at the heater connector (if no power, repair the connector of the heater switch).
     

  2.  
  3. If power exists at the pink wire, disconnect the heater connector and connect a tester across the harness terminal. If no power, repair the ground wire; if power exists, check the resistance of the heater.
  4.  
  5. If heater is over 3 ohms, replace the heater. If under 3 ohms, replace the connector, start the engine (operate to normal temperature) and probe the pink wire. If no power, the system is OK; if power exists, replace the heater switch.
  6.  

REMOVAL & INSTALLATION



Vacuum Servo Type
  1. Disconnect the vacuum hose at the EFE.
  2.  
  3. Remove exhaust pipe to manifold nuts.
  4.  
  5. Remove the crossover pipe. Complete removal is not always necessary.
  6.  
  7. Remove the EFE valve.
  8.  

To install:
  1. Position the EFE valve into place.
  2.  
  3. Install the crossover pipe.
  4.  
  5. Install the exhaust pipe to manifold nuts.
  6.  
  7. Connect the vacuum hose at the EFE.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of a vacuum servo EFE valve assembly

Electrical Type
  1. Remove the air cleaner and disconnect the negative battery cable.
  2.  
  3. Tag, then disengage all electrical, vacuum and fuel connections from the carburetor.
  4.  
  5. Disconnect the EFE heater electrical lead.
  6.  
  7. Remove the carburetor.
  8.  
  9. Lift off the EFE heater grid.
  10.  

To install:
  1. Position the EFE heater grid onto the manifold.
  2.  
  3. Install the carburetor.
  4.  
  5. Connect the EFE heater electrical lead.
  6.  
  7. Connect all electrical, vacuum and fuel connection to the carburetor.
  8.  
  9. Install the air cleaner and connect the negative battery cable.
  10.  



Click image to see an enlarged view

Fig. Fig. 2: Electric EFE heater assembly

Electric EFE Relay
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the retaining bracket.
  4.  
  5. Tag and disconnect all electrical connections.
  6.  
  7. Unscrew the retaining bolts and remove the relay.
  8.  

To install:
  1. Position the relay into place and secure the relay with the retaining bolt.
  2.  
  3. Attach all electrical connections.
  4.  
  5. Install the retaining bracket.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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