Remove the air cleaner. Disconnect the vacuum hose from the distributor.
On 1977–78 models, disconnect the vacuum control valve hose at the
intake manifold fitting, and install the distributor hose on that fitting.
On 1979 and later 49 States models, disconnect the anti-afterburn valve line
at the intake manifold fitting and install the distributor vacuum line to
the intake manifold fitting. On 1979 and later California models, disconnect
the air bypass valve hose from the intake manifold fitting and install the
distributor vacuum line to the intake manifold fitting.
Remove the vacuum hose from the carburetor side of the spark delay valve.
Plug this hose, and attach a vacuum gauge to the delay valve.
Start the engine and allow it to idle.
Disconnect the vacuum hose from the intake manifold fitting (the hose from
the spark delay valve to the distributor which has been connected to the intake
manifold in Step 2) and note the time for the vacuum gauge reading to drop
to 11.8 in. Hg. It should drop to this figure within 2–7 seconds (1–10
seconds on California models), 1977–78, or 4–6 seconds, 1979 and
later. If the reading is not correct, replace the spark delay valve.
After all tests have been completed, return the hoses to their original
positions.
