Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

Diesel Engines

Print

Due to the relative simplicity of the diesel engine compared to the gasoline engine, tune-up procedures consist of adjusting the valves, setting the maximum and minimum engine speeds and adjusting the throttle linkage (every 15,000 miles or 24,155 km), and taking a compression test (every 75,000 miles or 120,773 km).

Valve adjustment procedures are detailed in the Valve Lash Adjustment portion of this section.

IDLE SPEED ADJUSTMENT



The use of the correct special tools or their equivalent is REQUIRED for this procedure. To correctly set the idle speed, you will need either the Volvo Monotester and adapter No. 9950 or a suitable photoelectric tachometer. A gasoline engine tachometer by itself cannot be used on a diesel engine, because the diesel does not have an electronic ignition system.

  1. Connect a suitable tachometer to the engine and run the engine to normal operating temperature.
  2.  
  3. Idle speed should be 720-880 rpm.
  4.  
  5. If not, adjust the idle speed by loosening the locknut and turning the idle speed screw on the fuel injection pump.
  6.  
  7. Tighten the locknut and apply a dab of paint or thread sealer to the adjusting screw to prevent it from vibrating loose.
  8.  
  9. After adjusting idle speed and maximum engine speed, adjust the engine throttle linkage.
  10.  

MAXIMUM ENGINE SPEED ADJUSTMENT



The diesel engine is governed by the fuel injection pump so that engine rpms will not exceed 5,100-5,300 rpm. Because of the extremely high compression ratio (23.5:1) and the great stored energy diesel oil contains, the diesel engine cannot be run at the high rpm levels of modern gasoline engines, as it would place a tremendous strain on the pistons, wrist pins, connecting rods and bearings of the engine.

To correctly set the idle speed you will need either the Volvo Monotester and adapter No. 9950 or a suitable photoelectric tachometer. A gasoline engine tachometer by itself cannot be used on a diesel engine because the diesel does not have an electronic ignition system.

  1. Connect the tachometer and run the engine to normal operating temperature.
  2.  
  3. Run the engine to maximum speed by turning the cable pulley counterclockwise.
  4.  


WARNING
Do not race the engine longer than absolutely necessary.

  1. Maximum speed should be between 5100-5300 rpm.
  2.  
  3. If not, loosen the locknut and adjust using the maximum speed screw.
  4.  
  5. Tighten the locknut and apply a dab of paint or thread sealer to the adjusting screw to prevent it from vibrating loose.
  6.  


WARNING
Do not attempt to squeeze more power out of your diesel by extending the maximum speed.

  1. After adjusting the maximum speed, adjust the engine throttle linkage.
  2.  

THROTTLE LINKAGE ADJUSTMENT



See Figures 1, 2, 3, 4 and 5

If the engine is cold, the cold start device must be disengaged before the linkage can be adjusted. To disengage the cold start device, loosen screw (1) in the illustration, push the lever forward and turn the sleeve 90°


WARNING
Do not touch screw (2) in the illustration, or the cold start device will have to be reset on the test bench.

To adjust the linkage:
  1. Disconnect the link rod lever on the injection pump by unsnapping the plastic clamp on the ball joint of the link rod and pulling the lever off the socket on the accelerator arm.
  2.  
  3. Turn the plastic cable adjuster until the cable is stretched out but does not cause the pulley to move from its idle stop.
  4.  
  5. Have an assistant press the accelerator pedal to the floor and check to see that the pulley notch touches the maximum speed stop.
  6.  
  7. For manual transmission models, proceed to Step 8.
  8.  
  9. To adjust the kickdown cable on models with automatic transmissions, have an assistant press the accelerator pedal to the floor and measure how much inner cable is exposed on the kickdown cable. It should be exposed approximately 2.05 in. (52mm) between the end positions.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: Disconnect the cold start device as shown-do not loosen screw No. 2, or the cold start device will have to be reset on the test bench



Click image to see an enlarged view

Fig. Fig. 2: Disconnect the link rod lever and adjust the cable at its plastic adjuster



Click image to see an enlarged view

Fig. Fig. 3: Depress the accelerator, making sure the pulley notch touches the maximum speed stop



Click image to see an enlarged view

Fig. Fig. 4: Adjust the kickdown cable-automatic transmission models



Click image to see an enlarged view

Fig. Fig. 5: Maximum clearance between the pulley and maximum speed stop is 0.012 in. (0.3mm)

  1. Return the accelerator pedal to idle position. The kickdown cable should be stretched and the distance between the kickdown cable clip and the cable sheath should be 0.01-0.04 in. (0.25-1.00mm).
  2.  
  3. If either of these measurements are not correct, adjust them at the threaded end of the cable sheath.
  4.  
  5. On all models, connect the link rod to the injection pump accelerator arm.
  6.  
  7. Have an assistant press the accelerator pedal to the floor and adjust the link rod length so that the injection pump accelerator arm touches the maximum speed adjusting screw.
  8.  
  9. Return the accelerator pedal to the idle position and check to see that the accelerator arm touches the idle speed adjusting screw. If not, loosen and move the link rod ball joint in its oblong slot on the accelerator arm until the arm touches the idle speed adjusting screw. Tighten the ball joint.
  10.  
  11. Repeat Steps 9 and 10 until the linkage is correctly adjusted.
  12.  

A maximum clearance of 0.012 in. (0.3mm) is permitted between the pulley and the maximum speed stop.

  1. Connect the cold start device, if it was disengaged.
  2.  

 
label.common.footer.alt.autozoneLogo