Air Injection: Testing and Inspection

Thermovalve C

1. Warm engine to operating temperature (cooling fan comes on).

Checking Thermovalve C:

2. Attach a vacuum gauge to hose #27 at the steel tubing manifold as shown.
3. There should be no vacuum at idle.
4. If there is vacuum, replace thermovalve C and retest. If there is no vacuum at idle, valve is good and test is complete.

Air Suction Valve

1. Remove air cleaner cover and filter, then start engine and allow to reach normal temperature.
2. Check for a bubbling noise from the air suction port at idle, located in lower portion of air cleaner assembly. A bubbling noise should be heard.
3. If bubbling noise is heard, proceed to step 11. If bubbling noise is not heard, disconnect hose No. 5 from air suction cut-off diaphragm and check for vacuum.
4. If vacuum is present, replace air suction cut-off diaphragm and repeat test. If vacuum is not present, reconnect hose No. 5 and proceed to step 5.
5. Disconnect hose No. 32 routed from control box at vacuum hose manifold then check for vacuum at vacuum hose manifold. Vacuum should be present.
6. If vacuum is not present, check vacuum line No. 32. If satisfactory, replace air bleed valve B and repeat test. If vacuum is present, check voltage at air suction control solenoid valve.
7. If voltage is present, replace air suction control solenoid valve and repeat test. If voltage is not present, proceed to step 8.
8. Inspect vacuum switch C for proper operation, replace as required.
9. Check for voltage at control unit black/yellow wire connector with ignition switch On. If voltage is not present, check wiring for damage or defects.
10. Check for continuity between control unit brown/black wire and suitable ground. Continuity should be present.
11. Raise engine speed above 3500 RPM. A bubbling noise should be heard from air suction port.
12. If a bubbling noise is not heard, proceed to step 14. If a bubbling noise is heard, check for voltage at air suction control solenoid valve.
13. If voltage is not present, replace air suction control solenoid valve and repeat test. If voltage is present, refer to steps 8 through 10.
14. Heat air bleed valve to approximately 140°F with a suitable hot air gun. Bubbling noise should stop at idle.
15. If bubbling noise stops, test is complete. If bubbling noise does not stop, replace air bleed valve B.