What's this thing?
What is this vacuum doohickey and why does it have a rubber thingie between it and the vacuum lines? Googling the part number stamped on the plastic part tells me it is the Distributor System/ Vacuum Modulator Valve (DS/ VMV) PN- 560694...but I don't know what that means.
It looks like the vacuum lines could easily connect directly to the DS/VMV but instead there's a rubber thing between the lines and their connections on the DS/VMV. What's the rubber thing for? https://lh4.ggpht.com/_NUF7e4VZj88/TN...0/IMG_5665.JPG |
Re: What's this thing?
The lines can connect directly to it, but the way it is, it prevents you from screwing up which hose goes where. Kind of like a connector on a wiring harness.
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Re: What's this thing?
I'll have to look for markings on the rubber thing, that might be what that is.
So what is the DS/VMV? |
Re: What's this thing?
it basically controls emissions equipment... but that stuff became problematic when the vehicles got older.I have something similar on my Buick that was a PITA to find a replacement for when it failed.
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Re: What's this thing?
I now know exactly what it is.
From the 1980 Buick Advance Chassis Manual: The DS-VMV limits the distributor spark vacuum to a calibrated value until ported vacuum applied to the control port of the DS-VMV is greater than the calibration value. When the ported vacuum is greater than the calibration value, the distributor spark vacuum is equal to the ported vacuum signal. In short, it provides whichever vacuum source is greater (assuming that "calibrated value" means "value of the other vacuum source") to its output (the distributor vacuum advance). |
Re: What's this thing?
Update to the update:
On further reading I've found out that the original info I found calling it a DS-VMV is incorrect. It is actually the SAVM (Spark Advance Vacuum Modulator) Non Linear Valve. There are a few different components that connect exactly the same way but differ by application. The smaller manual I read first didn't describe as many as the larger manual I have since read. I'm more sure of this identification for these reasons:
From the manual: Quote:
Testing in plain English:
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