Toyota Celica/Supra 1971-1985 Repair Guide

Spark Control System (SCS)

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See Figures 1, 2, 3, 4 and 5



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Fig. Fig. 1: Vacuum hose routing on the spark control system-22R engine



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Fig. Fig. 2: Vacuum hose routing on the spark control system-5M-E engine



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Fig. Fig. 3: Schematic of the spark control system operation-5M-E engine



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Fig. Fig. 4: Schematic of the spark control system operation (continued)-5M-E engine



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Fig. Fig. 5: Spark control system operating conditions-5M-E engine

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.

TESTING



1979 Celica
FEDERAL MODELS

See Figure 6



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Fig. Fig. 6: Run the engine until it reaches normal operating temperature, then pinch the line between the TVTV and the advance port

  1. Connect a vacuum gauge to the line leading from the distributor advance diaphragm.
  2.  
  3. Start the engine.
  4.  
  5. Check that the vacuum reading changes quickly when the throttle valve is opened and closed. If it does not change, check the TVTV.
  6.  
  7. Run the engine until it reaches normal operating temperature and then pinch the line between the TVTV and the advance port.
  8.  
  9. Rev the engine to 2000 rpm and release the hose.
  10.  
  11. The reading on the vacuum gauge should be at least 4 in. Hg (13 kPa) within 2-4 seconds after releasing the hose.
  12.  
  13. With the engine speed maintained at 2000 rpm, check to see that the vacuum gauge indicates zero vacuum when the hose is disconnected from the advancer port. If it does not, check the TVTV.
  14.  
  15. Remove the TVTV and place its end in cool water. When blowing into one pipe, a large flow of air should be felt at the other one. Test both pipes in the same manner.
  16.  
  17. Heat the water to a temperature above 129°deg;F (54°deg;C). Blow into the vertical pipe. Air flow from the horizontal pipe should be good.
  18.  
  19. Blow into the horizontal pipe. Air flow from the vertical pipe should be minimal.
  20.  
  21. If the valve is not operating properly it will require replacement.
  22.  

CALIFORNIA MODELS

See Figures 7, 8 and 9



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Fig. Fig. 7: Check that the air flows without resistance from B to A. Resistance to air flow should be present from A to B



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Fig. Fig. 8: On cold engines, air flow on the TVSV should be as shown



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Fig. Fig. 9: With the engine warmed, the air flow on the TVSV should be as shown

  1. Connect a vacuum gauge to the line leading from the distributor advance diaphragm.
  2.  
  3. Start the engine.
  4.  
  5. Check that the vacuum reading changes quickly when the throttle valve is opened and closed. If it does not change, check the TVTV.
  6.  
  7. Run the engine until it reaches normal operating temperature and then pinch the line between the TVSV and the spark control port.
  8.  
  9. Maintain the engine speed at 2000 rpm; the vacuum gauge should indicate at least 4 in. Hg (13 kPa) within 2-4 seconds.
  10.  
  11. Release the hose. The gauge should indicate less that 4 in. Hg (13 kPa). If the preceding tests were positive, the procedure is finished. If not, inspect the TVSV and the VTV.
  12.  
  13. With the engine cold, blow into the pipe on the outside end of the TVSV. The air should come out of the middle pipe and the one on the side. No air should be felt coming out of the pipe on the inside end of the valve.
  14.  
  15. Run the engine until it reaches normal operating temperature and then blow into the middle pipe. The air should come out of the pipe on the side and the one on the inside end. No air should be felt coming from the pipe on the outside end of the valve. Replace the valve if it is not operating properly.
  16.  
  17. Remove the VTV and blow into the light colored side (A). The air should flow freely out of the other side.
  18.  
  19. Blow into the dark side of the valve (B). The flow of air coming out of the other side should be minimal. Replace the valve if it is not operating properly.
  20.  

1980-83 Celica

This procedure applies to carbureted vehicles only.

When performing Steps 1-7, remember that on 1980-81 Celicas there is no TVTV, only a VTV. The 1982-83 Celicas use a BVSV in place of the VTV. Substitute VTV and BVSV for TVTV whenever necessary.

  1. Connect a vacuum gauge to the line leading from the distributor advance diaphragm.
  2.  
  3. Start the engine.
  4.  
  5. Check that the vacuum reading changes quickly when the throttle valve is opened and closed. If it does not change, check the TVTV.
  6.  
  7. Run the engine until it reaches normal operating temperature and then pinch the line between the TVTV and the advance port.
  8.  
  9. Rev the engine to 2000 rpm and release the hose.
  10.  
  11. The reading on the vacuum gauge should be at least 4 in. Hg (13 kPa) within 2-4 seconds after releasing the hose.
  12.  
  13. With the engine speed maintained at 2000 rpm, check to see that the vacuum gauge indicates zero vacuum when the hose is disconnected from the advancer port. If it does not, check the TVTV.
  14.  
  15. Remove the VTV and blow into each side. Air should flow without resistance from the dark side to the light side WITH resistance from the light side to the dark side.
  16.  

1979-81 Supra

See Figure 10



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Fig. Fig. 10: When air is blown into the white pipe, the valve should be open. When air is blown into the black pipe, the valve should be closed

  1. Start the engine and connect a vacuum gauge to the hose leading from the inside half of the distributor diaphragm. The vacuum gauge should indicate high vacuum.
  2.  
  3. Run the engine until it reaches normal operating temperature. The gauge should indicate low vacuum. If the preceding tests were positive, the procedure is finished. If not, inspect the check valve and the BVSV.
  4.  
  5. Remove the check valve. When air is blown into the white pipe, the valve should be open. When air is blown into the black pipe, the valve should be closed.
  6.  
  7. Check the BVSV as detailed in the "Evaporative Emissions Control" information.
  8.  

 
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