GM Astro/Safari 1985-1996 Repair Guide

CMFI Assembly

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REMOVAL & INSTALLATION



Except 1996

See Figures 1 and 2



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Fig. Fig. 1: Exploded view of the upper and lower intake manifolds and the CMFI system components



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Fig. Fig. 2: Upper intake manifold torque sequence

The CMFI assembly is mounted to the lower intake manifold. The upper intake manifold assembly must be removed for access. The CMFI assembly includes a fuel meter body, gasket seal, fuel pressure regulator, fuel injector and 6 poppet nozzles with fuel tubes. Should a failure occur in any components of the CMFI unit, the entire assembly must be replaced.

  1. Remove the plastic cover and properly relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable, then remove the air cleaner and air inlet duct.
  4.  
  5. Disengage the wiring harness from the necessary upper intake components including:

    Throttle Position (TP) sensor
     
    Idle Air Control (IAC) motor
     
    Manifold Absolute Pressure (MAP) sensor
     
    Intake Manifold Tuning Valve (IMTV)
     

  6.  
  7. Disengage the throttle linkage from the upper intake manifold, then remove the ignition coil.
  8.  
  9. Disconnect the PCV hose at the rear of the upper intake manifold, then tag and disengage the vacuum hoses from both the front and rear of the upper intake manifold.
  10.  
  11. Remove the upper intake manifold bolts and studs, making sure to note or mark the location of all studs to assure proper installation. Remove the upper intake manifold from the engine.
  12.  
  13. Disengage the injector wiring harness connector at the CMFI assembly.
  14.  
  15. Remove and discard the fuel fitting clip.
  16.  
  17. Disconnect the fuel inlet and return tube and fitting assembly. Discard the old O-rings.
  18.  
  19. Squeeze the poppet nozzle locktabs together while lifting each nozzle out of the casting socket. Once all 6 nozzles are released, carefully lift the CMFI assembly out of the casting.
  20.  

To install:
  1. Align the CMFI assembly grommet with the casting grommet slots and push downward until it is seated in the bottom guide hole.
  2.  


CAUTION
To reduce the risk of fire and personal injury, be ABSOLUTELY SURE that the poppet nozzles are firmly seated and locked into their casting sockets. An unlocked poppet nozzle could work loose from its socket resulting in a dangerous fuel leak.

  1. Carefully insert the poppet nozzles into the casting sockets. Make sure they are FIRMLY SEATED and locked into the casting sockets.
  2.  
  3. Position new O-ring seals (lightly coated with clean engine oil), then connect the fuel inlet and return tube and fitting assembly.
  4.  
  5. Install a new fuel fitting clip.
  6.  
  7. Temporarily connect the negative battery cable, then pressurize the fuel system by cycling the ignition switch ON for 2 seconds, then OFF for 10 seconds and repeating, as necessary. Once the fuel system is pressurized, check for leaks.
  8.  
  9. Disconnect the negative battery cable.
  10.  
  11. Position a new upper intake manifold gasket on the engine, making sure the green sealing lines are facing upward.
  12.  
  13. Install the upper intake manifold being careful not to pinch the fuel injector wires between the manifolds.
  14.  
  15. Install the manifold retainers, making sure the studs are properly positioned, then tighten them using the proper sequence to 124 inch lbs. (14 Nm).
  16.  
  17. Connect the PCV hose to the rear of the upper intake manifold and the vacuum hoses to both the front and rear of the manifold assembly.
  18.  
  19. Connect the throttle linkage to the upper intake, then install the ignition coil.
  20.  
  21. Engage the necessary wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the IMTV.
  22.  
  23. Install the plastic cover, the air cleaner and air inlet duct.
  24.  
  25. Connect the negative battery cable.
  26.  

1996 CSFI

See Figures 3, 4 and 5



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Fig. Fig. 3: Exploded view of the CSFI system components



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Fig. Fig. 4: The CSFI unit mounts to the lower manifold



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Fig. Fig. 5: Exploded view of the CSFI components and manifolds

The 1996 4.3L engine is equipped with a sequential version of CMFI. It is very similar to the standard non-sequential CMFI except that there is a separate injector for each cylinder. This allows each cylinder to receive a timed pulse of fuel exactly when needed.

  1. Clean the upper manifold area and fuel meter body area before disassembly to help prevent dirt from entering the air intake tract when the manifold is removed.
  2.  
  3. Disconnect the negative battery cable. Relieve the fuel system pressure.
  4.  
  5. Disconnect the wiring from the fuel meter body.
  6.  
  7. Remove the fuel inlet and return pipes from the fuel meter body and upper manifold. Keep dirt from falling into the now open fuel ports on the meter body.
  8.  
  9. Remove the upper manifold from the lower section. The air inlet tract is now open to contamination, so stuff some rags into the openings to prevent dirt from falling in.
  10.  
  11. Mark the poppet valves relative to their cylinders. This will prevent mixing them up during installation.
  12.  
  13. Release the poppet valves from the lower manifold by squeezing the tabs together and pulling out.
  14.  
  15. Release the fuel meter body from the lower manifold by unlocking the tabs from the bracket and removing the bolts.
  16.  
  17. Pull up on the fuel meter body to remove it from the manifold.
  18.  

To install:
  1. Install the fuel meter body and tighten the bolts to 88 inch lbs. (10.0 Nm). Make sure the body has locked all the tabs in place.
  2.  
  3. Install the poppet valves into the bores in the same locations as they were removed. Be sure the tabs lock into place or fuel leakage will occur.
  4.  
  5. Install the upper intake manifold electrical connector.
  6.  
  7. Install new O-rings on the fuel lines. Install the fuel lines on the manifold and tighten the connections to 22 ft. lbs. (30.0 Nm).
  8.  
  9. Connect the negative battery cable. Turn the ignition switch ON for 2 seconds, OFF for 10 seconds, ON for 2 seconds and then OFF again. Check for leaks from the fuel connections. Fix as necessary.
  10.  
  11. Disconnect the negative battery cable and the fuel lines.
  12.  
  13. Install the upper intake manifold.
  14.  
  15. Connect the fuel lines and check the fuel meter body electrical connection.
  16.  
  17. Connect the negative battery cable.
  18.  

 
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