GM Cadillac 1967-1989 Repair Guide

Adjustments For Diesel Engines

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See Figures 1, 2 and 3

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 (THM 350's only) on 1979 and later models requires the use of several special tools.

THROTTLE ROD ADJUSTMENT

  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 (THM 200) or detent cable (THM 350) 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.  
  9. Tighten the throttle rod locknut.
  10.  
  11. Connect the throttle valve or detent cable and cruise control rod to the bellcrank. Adjust if necessary.
  12.  

THROTTLE VALVE (TV) OR DETENT CABLE ADJUSTMENT



Refer to the previous cable adjustment procedures for gasoline engines. Adjust according to the style of cable which is used.



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Fig. Fig. 1: Diesel engine throttle linkage



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Fig. Fig. 2: Transmission vacuum valve adjustment - 1978 diesel models



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Fig. Fig. 3: 1979 and later diesel transmission vacuum valve adjustment

TRANSMISSION VACUUM VALVE ADJUSTMENT



1978 Models
  1. Remove the throttle rod from the bellcrank.
  2.  
  3. Loosen the transmission vacuum valve attaching bolts just enough to disengage the valve from the injection pump shaft.
  4.  
  5. Hold the injection pump lever against the full throttle stop.
  6.  
  7. Rotate the valve to the full throttle position, then insert a 3 / 32 in. (2.38mm) diameter pin to hold the valve in the full throttle position.
  8.  
  9. Rotate the assembly clockwise until the injection pump lever is contacted.
  10.  
  11. While holding the assembly in contact with the lever, tighten the two bolts holding the vacuum valve to the pump, remove the pin and release the lever, then reconnect the throttle rod to the bellcrank.
  12.  

1979 and Later Models

See Figures 4, 5 and 6

  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.  
  13. Turn the throttle lever to the wide open throttle position. Set the angle gauge to zero degrees.
  14.  
  15. Center the bubble in the gauge level.
  16.  
  17. Set the angle gauge to the proper settings, according to the year and type of engine as indicated by the chart.
  18.  
  19. Attach a vacuum gauge to port 2 and a vacuum source (e.g. hand-held vacuum pump) to port 1 of the vacuum valve.
  20.  
  21. Apply 18-22 in. of vacuum to the valve. Slowly rotate the valve until the vacuum reading drops to the appropriate values, again as indicated by the vacuum gauge reading chart.
  22.  
  23. Tighten the vacuum valve retaining bolts.
  24.  
  25. Reconnect the original vacuum lines to the vacuum valve.
  26.  
  27. Remove the angle gauge and adapter.
  28.  
  29. Connect the throttle rod to the throttle lever.
  30.  
  31. Install the air intake crossover, using new gaskets.
  32.  
  33. Install the air cleaner assembly.
  34.  



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Fig. Fig. 4: Angle gauge settings



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Fig. Fig. 5: Vacuum gauge readings



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Fig. Fig. 6: Angle gauge installation (with adapter) for diesel vacuum valve adjustment - the gauge is positioned differently, depending on the type of throttle lever used

 
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