GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Early Fuel Evaporation (EFE) Heater

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The EFE heating system is used on all carbureted engines. The purpose of the heating unit is to further vaporize the fuel droplets as they enter the intake manifold; vaporization of the air/fuel mixture ensures complete combustion which provides the maximum power and minimum emissions output for the fuel used.

REMOVAL & INSTALLATION



Heater Unit

See Figures 1, 2, 3 and 4

The EFE heater unit is located directly under the carburetor and is electrically operated.



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Fig. Fig. 1: Common EFE heater unit installation - 2.8L shown

  1. Disconnect the negative battery terminal, then remove the air cleaner assembly.
  2.  
  3. From the carburetor, tag and disconnect the vacuum hoses, electrical wiring and fuel hoses. Disengage the EFE heater electrical connector from the wiring harness.
  4.  
  5. Remove the carburetor-to-intake manifold retainers, then carefully remove the carburetor from the manifold.
  6.  



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Fig. Fig. 2: Disengage the EFE wiring connector



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Fig. Fig. 3: Carefully lift the EFE from the intake manifold

Be careful once the carburetor is removed from the manifold not to allow anything (bolts, debris) to fall into the opening or the manifold may have to be removed.

  1. Lift the EFE heater unit from the intake manifold.
  2.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces.
  2.  

During installation, replace all gaskets to assure proper sealing and to prevent vacuum leaks.

  1. Position the EFE heater unit to the intake manifold.
  2.  



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Fig. Fig. 4: When cleaning the intake manifold gasket mounting surface, cover the opening to keep debris out of the engine

  1. Install the carburetor to the intake, then tighten the carburetor-to-intake manifold retainers to 13 ft. lbs. (18 Nm).
  2.  
  3. Engage the EFE wiring connector to the harness.
  4.  
  5. Connect the fuel hoses, electrical wiring and vacuum hoses as noted during removal.
  6.  
  7. Install the air cleaner assembly and connect the negative battery terminal.
  8.  

Heater Switch

See Figures 5, 6 and 7

The heater switch is located near the thermostat housing (2.8L carbureted engine), on the bottom rear-side of the intake manifold (2.0L carbureted engine) or on the top right-side of the engine (1.9L carbureted engine).

  1. Position a drain pan under the radiator, then open the drain cock and drain the coolant to a level below the heater switch.
  2.  
  3. Disengage the wiring harness connector from the EFE heater switch.
  4.  
  5. Remove the EFE heater switch (turn it counterclockwise) from the intake manifold.
  6.  

To install:
  1. Coat the threads of the EFE heater switch with a soft setting sealant, then thread it into the intake and tighten to 10 ft. lbs. (14 Nm).
  2.  

When applying sealant to the EFE heater switch threads, be careful not to coat the sensor and/or the switch.

  1. Reconnect the wiring harness to the EFE heater switch.
  2.  
  3. Properly refill the cooling system. Coolant can be reused unless it is several years old or appears contaminated.
  4.  



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Fig. Fig. 5: EFE heater switch installation - 2.8L engine



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Fig. Fig. 6: EFE heater switch installation - 2.0L engine



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Fig. Fig. 7: EFE heater and switch - 1.9L engine

Heater Switch Relay

See Figures 8 and 9

The heater switch relay is usually located on the left-fender.

  1. Disconnect the negative battery terminal.
  2.  
  3. Disengage the wiring harness connector(s) from the heater switch relay.
  4.  
  5. Remove the heater switch relay-to-bracket screw, then remove the relay from the truck.
  6.  
  7. To install, reverse the removal procedures.
  8.  



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Fig. Fig. 8: EFE heater switch relay - 2.8L engines



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Fig. Fig. 9: Common EFE heater switch relay used on later model carbureted engines

 
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