Vacuum Supply Test

VACUUM SUPPLY TEST

NOTE: The vacuum supply to the vacuum diaphragm unit and the diaphragm itself must be checked.

1. Disconnect vacuum line at diaphragm unit and connect suitable vacuum gauge.

NOTE: With engine idling, the gauge must show a steady acceptable vacuum for the altitude at which the test is being performed.

2. If vacuum reading is low, check for a vacuum leak or poor engine vacuum.
3. If vacuum reading is satisfactory, rapidly accelerate engine momentarily.
a. Vacuum reading must drop rapidly at acceleration and return immediately upon release of acceleration.
b. If vacuum does not change or changes slowly, the transmission vacuum line is plugged, restricted, or connected to a reservoir supply. Correct as necessary.