Quote:
Originally Posted by qpoiz
My questions arise with the following. I understand how the VCV is supposed to work. It leaks vacuum at a controlled rate depending on throttle position. But when i test for vacuum, it only holds vacuum from the TOP of the vcv, not from the side, where the vacuum originates.
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Your understanding of how it operates is flawed.
The vacuum source is on the top of the valve. The side of the valve is atmosphere............leads into the cabin as a vent line.
When the valve operates, it draws air from the cabin through the side port, through the valve, and into the line at the top. The line at the top is teed into the transmission line so that the entire line downstream of the orifice will lose vacuum when the VCV opens.
The VCV should hold about 13" vacuum when you use a Mityvac connected to the top port. As you open the rack, this vacuum level will gradually drop toward zero depending on the amount of the opening.