See Figures 1 and 2

The spark control system is used to reduce the NOx and HC emissions. The system serves to delay the vacuum advance for a given time, while also lowering the maximum combustion temperature.



Click image to see an enlarged view

Fig. Fig. 1: Spark Control (SC) system components-except California models



Click image to see an enlarged view

Fig. Fig. 2: Spark control system components used on California models

TESTING

Vacuum Advancer

See Figure 3

  1. Remove the distributor cap and rotor.
    2.  
  2. Apply vacuum to the retard diaphragm, then the advance diaphragm. Check that the vacuum advancer moves in accordance with the vacuum.
    3.  



Click image to see an enlarged view

Fig. Fig. 3: Check the vacuum advance mechanism for movement when vacuum is applied

  1. If a problem is found, replace the vacuum advancer. Install the cap and rotor.
    2.  

Check Valve

See Figure 4

  1. Check that air flows from side A of the valve to side B.
    2.  



Click image to see an enlarged view

Fig. Fig. 4: Air should flow from side A to B, but not from side B to A

  1. Check that air does not flow from side B to side A. If the valve is not in working order, replace it.
    2.  

Bi-Metal Vacuum Switching Valve (BVSV)
  1. Drain the coolant from the radiator into a suitable container.
    2.  
  2. Remove the BVSV.
    3.  
  3. Cool the BVSV in water below 104°F (40° C).
    4.  
  4. Blow air into a pipe and check that the BVSV is closed.
    5.  
  5. Heat the valve in water above 129° F (54° C).
    6.  
  6. Blow air into the pipe and check that the valve is open.
    7.  
  7. Apply liquid sealer to the first few threads of the valve and reinstall it in the engine.
    8.  
  8. Fill the radiator with coolant and water mixture. Start the engine and check for leaks.
    9.  
  9. If a problem is found with the testing of the BVSV, replace the valve.
    10.