Electronic Vacuum Regulator (EVR) Repair

Has anyone ever taken an Electronic Vacuum Regulator apart?
I was getting a 172 (EEC-IV) fault code, which indicates "system weak". A vacuum pump revealed that the EVR solenoid (which controls vacuum to
the EGR valve) would not hold vacuum whether it was energised or not. Clamping the vacuum feed to the EVR caused the 172 to go away (although I did get a code inidicating "EGR valve not opening").
Taking the EVR apart I find that it has very few parts. A coil acts on a metal disk to cover or uncover the outlet port. But, it doesn't seem to be air tight. There is no seal around the disk. Also the disk is held against the solenoid coil by a spring. I suppose vacuum might pull it away from the coil but there is nothing for it to seal against. It's seat even has raised lands to, it would appear, allow some leakage of vacuum.
Anyone know what's going on?
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snipped-for-privacy@mailshack.com wrote:

Yes Neil, the EVR doesn't totally block vacuum when "at rest". It allows a bit of a vacuum leak to atmosphere. When energized, it sends vacuum to the EGR valve. Even then, it's not a "perfect" vacuum. I have to ask, why are you dismantling your EGR solenoid? Fault code, by chance?
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Tom Adkins wrote:

As I said I was getting a 172 code: "System Weak"
The vacuum system appears tight (unless there is another takeoff I haven't found) except for the feed to the Pulse Air and EGR system solenoids. The pulse air holds vacuum, but the EGR doesn't. The EGR therefore seems a bit hit and miss. Also, sadly, the manual I am using says that it should hold vacuum. I've got a new one, which I am about to fit. I will then see if I have a 172 code or not.
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