Vacuum Advance
- With distributor in test stand, check advance at vacuum settings shown in specifications. See appropriate DISTRIBUTOR ADVANCE SPECIFICATIONS table in this section. Replace vacuum unit if tests indicate vacuum diaphragm unit is inoperative, out of calibration, or leaking.
- Most types of vacuum diaphragm units are factory pre-set and cannot be adjusted. However, on some dual diaphragm vacuum units, vacuum advance may be increased or decreased by turning an Allen screw located on end of diaphragm unit.