Testing of Air Bleed Technicians testing a Choke Pull-off equipped with air bleed holes are reminded that a large volume vacuum source such as engine manifold vacuum should be used. A hand-held vacuum pump is insufficient for testing. When a manifold vacuum source is attached to this style of Choke Pull-off, retraction of the plunger will occur in approximately 2 to 3 seconds. The air bleed hole is present to dampen the rate of plunger retraction, preventing a start-up and stall condition. Visit our Resource Library for available downloads