GM Caprice 1990-1993 Repair Guide

Early Fuel Evaporation (EFE)

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See Figure 1



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Fig. Fig. 1: EFE system - vacuum servo type

OPERATION



The EFE system is used on the 5.0L (VIN Y) engine 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.

The Vacuum Servo type consists of a valve, an actuator and a Thermal Vacuum Switch (TVS)-the valve is located in the exhaust manifold and the TVS switch is on the engine coolant housing.

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

SYSTEM CHECK



  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 or replace the valve.
  8.  

REMOVAL & INSTALLATION



  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.  
  9. To install, position the EFE valve into place.
  10.  
  11. Install the crossover pipe.
  12.  
  13. Install the exhaust pipe to manifold nuts.
  14.  
  15. Connect the vacuum hose at the EFE.
  16.  

 
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