GM Firebird 1967-1981 Repair Guide

Early Fuel Evaporation (EFE) System

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GENERAL INFORMATION 1975 and Later Models (Except Turbo)



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the EFE valve mounting (non-turbocharged model)

This is a more effective form of heat riser which is vacuum actuated. It is used on Firebirds built in 1975 and later. It heats incoming mixture during the engine warm-up process, utilizing a ribbed heat exchanger of thin metal that is located in the intake manifold. This pre-heating allows the choke to open more rapidly, thus reducing emissions. Problems in this system might be indicated by poor engine operation during warm-up.

This valve should be checked initially at 6 months/7500 miles, and at 18 month/22,500 mile intervals thereafter.

To check, move the valve through its full stroke by hand, making sure that the linkage does not bind and is properly connected. If the valve sticks, free it up with solvent. Also check that all vacuum hoses are properly connected and free of cracks or breaks. Replace hoses or broken or bent linkage parts as necessary.

Turbo Models See Figure 2

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Fig. Fig. 2: The EFE heater on a turbocharged engine is mounted between the carburetor and the plenum assembly

Although the function of the EFE system used on these models remains the same to reduce engine warm-up time, improve driveability and to reduce emissions the operation is entirely different. The new system is electric and uses a ceramic heater grid located underneath the carburetor as part of the carburetor insulator/gasket. When the engine coolant is below the specified calibration level, electrical current is supplied to the heater through an Electronic Control Module (ECM) controlled relay.

REMOVAL & INSTALLATION Turbo Models



EFE GRID
  1. Remove the air cleaner.
  2.  
  3. Detach all electrical, vacuum and fuel connections from the carburetor.
  4.  
  5. Detach the EFE heater electrical connection.
  6.  
  7. Remove the carburetor as detailed in Driveability And Emissions Controls .
  8.  
  9. Lift off the EFE heater grid.
  10.  
  11. Installation is in the reverse order of removal.
  12.  

EFE HEATER RELAY
  1. Disconnect the negative battery cable.
  2.  
  3. Tag and detach all electrical connections.
  4.  
  5. Unscrew the retaining bolts and remove the relay.
  6.  
  7. Installation is in the reverse order of removal.
  8.  

 
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