Chevrolet Citation/Omega/Phoenix/Skylark 1980-1985 Repair Guide

Early Fuel Evaporation (EFE) System



1980 Vehicles

All V6 engines have this system to reduce engine warm-up time, improve driveability, and reduce emissions. On start-up, a vacuum motor acts to close a heat valve in the exhaust manifold, which causes exhaust gases to enter the intake manifold heat riser passages. The incoming fuel mixture is thus heated, resulting in more complete fuel evaporation. When the engine warms up, the valve opens. Vacuum to the EFE valve is controlled by a Thermal Vacuum Switch (TVS) installed in the intake manifold, which monitors engine coolant temperatures and permits or restricts manifold vacuum to the valve accordingly.

Service procedures for this system are covered in Section One.

1981-85 Vehicles

As in 1980, only V6 engines utilize this system. Although the function of the 1981 EFE system 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 primary bore of 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 ECM controlled relay.


EFE Heater Grid

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Fig. Fig. 1 The EFE heater grid, on 1981-85 vehicles, is under the carburetor

  1. Remove the air cleaner.
  3. Disconnect all electrical, vacuum and fuel connections from the carburetor.
  5. Disconnect the EFE heater electrical connection.
  7. Remove the carburetor as detailed later in this section.
  9. Lift off the EFE heater.
  11. Installation is in the reverse order of removal.
  13. Start the engine and check for any fuel leaks.

EFE Heater Relay

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Fig. Fig. 2 The EFE heater relay can be found on the right side radiator support

  1. Disconnect the negative battery cable.
  3. Tag and disconnect all electrical connections.
  5. Unscrew the retaining bolts and remove the relay.
  7. Installation is in the reverse order of removal.