GM Cutlass RWD 1970-1987 Repair Guide

Diesel Engine Adjustments

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Before making any linkage adjustments, check the injection timing, and adjust if necessary. Also note that these adjustments should be performed together. The vacuum valve adjustment (THM350's only) on 1979 and later models requires the use of several special tools. If you do not have these tools at your disposal, refer the adjustment to a qualified, professional technician.

THROTTLE ROD



See Figures 1 and 2

  1. If equipped with cruise control, remove the clip from the control rod, then remove the rod from the bellcrank.
  2.  
  3. Remove the throttle valve cable (THM200) or detent cable (THM350) from the bellcrank.
  4.  
  5. Loosen the locknut on the throttle rod, then shorten the rod several turns.
  6.  
  7. Rotate the bellcrank to the full throttle stop, then lengthen the throttle rod until the injection pump lever contacts the injection pump full throttle stop. Release the bellcrank.
  8.  



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Fig. Fig. 1: Diesel throttle adjustment



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Fig. Fig. 2: Diesel throttle valve cable adjustment

  1. Tighten the throttle rod locknut.
  2.  
  3. Connect the throttle valve or detent cable and cruise control rod to the bellcrank. Adjust if necessary.
  4.  

THROTTLE VALVE CABLE OR DETENT CABLE



  1. Remove the throttle rod from the bellcrank.
  2.  
  3. Push the snap lock to the disengaged position.
  4.  
  5. Rotate the bellcrank to the full throttle stop and hold it there.
  6.  
  7. Push in the snap lock until it is flush with the cable end fitting. Release the bellcrank.
  8.  
  9. Reconnect the throttle.
  10.  

VACUUM VALVE



See Figures 3 and 4

1981 and Later Models
  1. Remove the air cleaner assembly.
  2.  
  3. Remove the air intake crossover from the intake manifold. Cover the intake manifold passages to prevent foreign material from entering the engine.
  4.  
  5. Disconnect the throttle rod from the injection pump throttle lever.
  6.  
  7. Loosen the transmission vacuum valve-to-injection pump bolts.
  8.  
  9. Mark and disconnect the vacuum lines from the vacuum valve.
  10.  
  11. Attach a carburetor angle gauge adapter (Kent-Moore tool J-26701-15 or its equivalent) to the injection pump throttle lever. Attach an angle gauge (J-26701 or its equivalent) to the gauge adapter.
  12.  



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Fig. Fig. 3: Vacuum regulator valve with an angle gauge attached and set to zero degrees

To service the V6 diesel, it may be necessary to file the gauge adapter in order for it to fit the thicker throttle lever of the V6 injection pump.

  1. Turn the throttle lever to the wide open throttle position. Set the angle gauge to zero degrees.
  2.  
  3. Center the bubble in the gauge level.
  4.  
  5. Set the angle gauge to the correct setting, according to the year and type of engine:
  6.  
  7. Attach a vacuum gauge to port 2 and a vacuum source (e.g. hand-held vacuum pump) to port 1 of the vacuum valve (as illustrated).
  8.  
  9. Apply 18-22 in. Hg (124-151 kPa) of vacuum to the valve. Slowly rotate the valve until the vacuum reading drops to the correct value.
  10.  
  11. Tighten the vacuum valve retaining bolts.
  12.  



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Fig. Fig. 4: Set the angle gauge to one of the following settings

  1. Reconnect the original vacuum lines to the vacuum valve.
  2.  
  3. Remove the angle gauge and adapter.
  4.  
  5. Connect the throttle rod to the throttle lever.
  6.  
  7. Install the air intake crossover, using new gaskets.
  8.  
  9. Install the air cleaner assembly.
  10.  

 
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