System Testing

1. Start engine and run until it reaches normal operating temperature, then ensure that idle speed is within specifications.
2. Determine position of HAC valve by blowing air into any of the ports on top of valve.
3. Air should pass easily through valve in high altitude position, and air should not pass through valve in low altitude position. If valve action does not correspond to ambient conditions (altitude), HAC valve is defective.
4. Test system with valve in high altitude position as follows:
a. Disconnect and plug vacuum hose at distributor sub-diaphragm port and ensure that ignition timing is within specifications.
b. Reconnect hose to sub-diaphragm port while observing ignition timing. Timing should advance.
c. Disconnect and plug vacuum hose between manifold and check valve at check valve while observing ignition timing. Timing should remain advanced for at least one minute.
d. Stop engine and reconnect hoses, then disconnect hoses from top of HAC valve.
e. Blow air into hoses and ensure that air flows through carburetor.
f. Reconnect air hoses.
5. Test system with valve in low altitude position as follows:
a. Disconnect and plug vacuum hose at distributor sub-diaphragm port, then check that ignition timing is within specifications.
b. Reconnect hose to sub-diaphragm port while observing ignition timing. Timing should advance.
c. Disconnect and plug vacuum hose from lowest port of HAC valve.
d. Disconnect and plug vacuum hose between manifold and check valve at check valve while observing ignition timing. Timing should remain advanced for at least one minute.
e. Stop engine and reconnect hoses, then disconnect hoses from top of HAC valve.
f. Blow air into hoses and ensure air flows through carburetor.
g. Reconnect air hoses.