Re: [DML] engine component testing.

["Walter" <Whalt@xxxx>]

Graham,

The thermal vacuum control valve works as an 'either/or' switch between the
control pressure regulator and the distributor vacuum advance. When cooler
than 40°C (104°F) it allows manifold vacuum to reach the control pressure
regulator but not the solenoid. When warmer than 40°C (104°F) the opposite
is the case: It allows no vacuum to reach the control pressure regulator
and does allow it to reach the solenoid.

Since your valve does not change states according to temperature, it appears
to be defective. Make sure that you are warming the valve up enough to
check it. Since your engine is not in running condition, what are you doing
to heat the valve?

If the valve is continually stuck in the cold state, then your spark will
not be advancing properly and this would not be good.

Hope this helps,
Walt Tampa, FL