Repair Pontiac Mid-size 1974-1983 Repair Guide

Diesel Engine Transmission




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. If you do not have these tools at your disposal, refer the adjustment to a qualified, professional technician.

Throttle Rod

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Fig. Fig. 1 Exploded view of the throttle linkage on diesel engines

  1. If equipped with cruise control, remove the clip from the control rod, then remove the rod from the bellcrank.
  3. Remove the throttle valve cable (THM 200) or detent cable (THM 350) from the bellcrank.
  5. Loosen the locknut on the throttle rod, then shorten the rod several turns.
  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.
  9. Tighten the throttle rod locknut.
  11. Connect the throttle valve or detent cable and cruise control rod to the bellcrank. Adjust if necessary.

Throttle Valve (TV) or Detent Cable

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Fig. Fig. 2 Diesel engine throttle valve cable adjustment

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

Transmission Vacuum Valve

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Fig. Fig. 3 Angle gauge mounting (with adapter) for diesel vacuum valve adjustment. The gauge is positioned differently, depending upon the type of throttle lever used

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Fig. Fig. 4 Diesel engine transmission vacuum valve adjustment-1979-83 vehicles

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Fig. Fig. 5 Specifications for setting the angle gauge

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Fig. Fig. 6 Vacuum reading specifications

1979-83 MODELS

A special angle gauge adaptor is needed for this procedure.

  1. Remove the air cleaner assembly.
  3. Remove the air intake crossover from the intake manifold. Cover the intake manifold passages to prevent foreign material from entering the engine.
  5. Disconnect the throttle rod from the injection pump throttle lever.
  7. Loosen the transmission vacuum valve-to-injection pump bolts.
  9. Mark and disconnect the vacuum lines from the vacuum valve.
  11. Attach a carburetor angle gauge adapter (Kent-Moore tool J-26701-15 or its equivalent) to the injection pump throttle lever. Attach the angle gauge (J-26701 or its equivalent) to the gauge adapter.
  13. Turn the throttle lever to the wide open throttle position. Set the angle gauge to zero degrees.
  15. Center the bubble in the gauge level.
  17. Set the angle gauge to one of the following settings, according to the year and type of engine, as shown in the accompanying figure.
  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 (as illustrated).
  21. Apply 18-22 in. Hg of vacuum to the valve. Slowly rotate the valve until the vacuum reading drops to one of the values shown in the accompanying figure.
  23. Tighten the vacuum valve retaining bolts.
  25. Reconnect the original vacuum lines to the vacuum valve.
  27. Remove the angle gauge and adapter.
  29. Connect the throttle rod to the throttle lever.
  31. Install the air intake crossover, using new gaskets.
  33. Install the air cleaner assembly.