Vacuum Control Valve

1978 4M Engine & 1981 22R Engine
1. Open and close throttle valve.
2. Check that compressed air is discharged from hose to front pipe of catalytic converter.

Fig.68 - Testing Vacuum Control Valve:

1978-79 20R Engine
1. Start engine.
2. Disconnect vacuum sensing hose, pipe "S", from vacuum control valve and reconnect it, Fig. 68.
3. Check that compressed air is momentarily discharged from by-pass hose.

1979 4M ENGINE

Vacuum Control Valve No. 1
1. To test vacuum control valve on car, proceed as follows:

a. Open and close throttle valve.
b. Check that compressed air is discharged from hose to front pipe of catalytic converter.

2. To test vacuum control valve off car, proceed as follows:

a. Remove vacuum control valve.
b. Remove filter cover and take out filter, visually check filter, and replace if damaged or clean filter by blowing with compressed air.
c. Install filter with thicker side positioned outward.
d. Install valve, being sure it is positioned in correct direction.
e. Connect vacuum gauge between valve and carburetor using 3-way fitting.
f. Disconnect hose from filter side of valve.
g. Check that valve is closed when engine vacuum is below 18.3 in. Hg.
h. Check that valve is open when engine vacuum is above 19.5 in. Hg.
i. Reconnect vacuum hose.

Fig.69 - Testing Vacuum Control Valve:

Vacuum Control Valve No. 2
1. To check vacuum passage in valve, proceed as follows:

a. Blow air into pipe "V", Fig. 69, and check that a large amount of air flows to pipes "Y" and W".
b. Close off pipes "Y" and "W" and check that a small amount of air flows to pipe"Z".
c. Reconnect hoses to proper location.

2. To test valve operation, proceed as follows:

Fig.70 - Testing Vacuum Control Valve:

a. Connect vacuum gauge using 3-way connector between port "Z" of valve and air switching valve, Fig. 70. Gauge should indicate high vacuum at idle.
b. Gradually increase engine speed to 5000 RPM. Vacuum gauge should indicate zero at approximately 5000 RPM.
c. Disconnect vacuum gauge and reconnect hose.

1981-82 3T-C ENGINE

Fig.71 - Testing Vacuum Valve:

Vacuum Control Valve No. 1
1. Disconnect vacuum hose from port "Z" and install vacuum gauge, Fig. 71.
2. Check that gauge indicates approximately 7.87 in. Hg. at idle.

Fig.72 - Testing Vacuum Control Valve:

Vacuum Control Valve No. 2
1. Disconnect vacuum hose from port "Y" and "Z", Fig. 72.
2. Check that small amount of air flows from port "Z" to port "Y".
3. Disconnect hose from port "S" and check that a large amount of air flows from port "Z" to port "Y".

Fig.73 - Testing Vacuum Control Valve:

Vacuum Control Valve No. 3
1. Disconnect vacuum hose from pert "Z" and port "S", Fig. 73.
2. Check that vacuum is not present at port "Z" with engine at idle.
3. Check for momentary vacuum at port "Z" as vacuum hose is connected to port "S".