GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

DCH340 Carburetor

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The DCH340 carburetor should be found on the 1.9L engine which was installed in early model trucks covered by this manual.

ADJUSTMENTS



Please refer toChapter 2 of this manual for Idle Speed and Mixture Adjustment procedures.

Float Level

See Figure 1

The fuel level is normal if it is seen to be within the mark on the float bowl window. If not, remove the top of the carburetor and bend the float seat to regulate the level.



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Fig. Fig. 1: Adjusting the float level-1.9L engine

Primary Throttle Valve

See Figure 2

When the choke plate is completely closed, the primary throttle valve should be opened by the fast idle screw to an angle of 16° (M/T) or 18° (A/T). To check this adjustment:

  1. Close the choke plate completely, then measure between the throttle plate and the air horn wall; the clearance should be 0.050-0.059 in. (1.3-1.5mm), M/T or 0.059-0.069 in. (1.50-1.75mm), A/T.
  2.  

The measurement should be made at the center point of the choke plate.

  1. If necessary, adjust the opening by turning the fast idle screw.
  2.  



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Fig. Fig. 2: Adjusting the primary throttle valve

Throttle Linkage

See Figure 3

  1. Turn the primary throttle valve plate until the adjustment plate is in contact with the kickdown lever. This is a primary throttle plate opening of about 47°.
  2.  
  3. Measure the clearance between the center point of the primary throttle plate and the air horn wall; the clearance should be 0.24-0.30 in. (6.0-7.6mm). If not, bend the kickdown lever tab.
  4.  



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Fig. Fig. 3: Adjusting the throttle linkage

Kickdown Lever

See Figure 4

  1. Turn the primary throttle lever until the plate is completely closed. Back off the throttle adjustment screw, if necessary.
  2.  
  3. Loosen the locknut on the kickdown lever screw and turn the screw until it just contacts the return plate, then tighten the locknut.
  4.  



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Fig. Fig. 4: Adjusting the kickdown lever

REMOVAL & INSTALLATION



See Figure 5

The DCH340 carburetor should be found on the 1.9L engine which was installed in early model trucks covered by this manual.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the PCV valve from the rocker arm cover.
  4.  
  5. Disconnect the ECS hose from the air cleaner.
  6.  
  7. Disconnect the AIR hose from the pump.
  8.  
  9. On California models, disconnect the air hose from the slow actuator.
  10.  
  11. Unbolt the air cleaner, lift it slightly, disconnect the hoses and remove the unit.
  12.  
  13. Disconnect the rubber piping from the TVS switch.
  14.  
  15. Disconnect the vacuum advance hose (if equipped) from the distributor.
  16.  
  17. If equipped with an A/T, disconnect the vacuum hose from the converter housing.
  18.  
  19. On California models, disconnect the vacuum hoses from the slow and main actuators.
  20.  
  21. Disconnect the carburetor solenoid lead wire, the accelerator control cable and the cruise control cable.
  22.  
  23. On automatic transmission models, disconnect the control cable.
  24.  
  25. Disconnect the fuel line(s) from the carburetor.
  26.  
  27. Disconnect the ECS hose from the carburetor.
  28.  
  29. Remove the carburetor-to-intake manifold bolts and the carburetor; discard the mounting gasket.
  30.  

Be sure to cover the opening in the intake manifold to prevent debris, foreign material or even a mishandled bolt from entering the engine.

Click image to see an enlarged view

Fig. Fig. 5: Exploded view of the DHC340 carburetor-1.9L engine

To install:
  1. Install the carburetor using a new gasket and secure using the carburetor-to-intake manifold bolts.
  2.  
  3. Connect the ECS hose to the carburetor.
  4.  
  5. Connect the fuel line(s) to the carburetor.
  6.  
  7. On automatic transmission models, connect the control cable.
  8.  
  9. Connect the carburetor solenoid lead wire, the accelerator control cable and the cruise control cable.
  10.  
  11. On California models, connect the vacuum hoses to the slow and main actuators.
  12.  
  13. If equipped with an A/T, connect the vacuum hose to the converter housing.
  14.  
  15. Connect the vacuum advance hose (if equipped) to the distributor.
  16.  
  17. Connect the rubber piping to the TVS switch.
  18.  
  19. Position the cleaner and connect the hoses, then secure it in position.
  20.  
  21. On California models, connect the air hose to the slow actuator.
  22.  
  23. Connect the AIR hose to the pump.
  24.  
  25. Connect the ECS hose to the air cleaner.
  26.  
  27. Install the PCV valve to the rocker arm cover.
  28.  
  29. Connect the negative battery cable.
  30.  
  31. Make sure all of the linkage is properly adjusted and operates smoothly. Check that there are no leaks.
  32.  
  33. Start and run the engine, then check and adjust the idle speed, as necessary.
  34.  

 
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