Gabriel Pennella

Hello, Mike,
I own a 74 911, and have the same problem some time
ago.
The 74 911 is the only one that has these control
pressure regulator, because the warm up regulator does
not have a vacuum line.
The 1975-onwards models, has a warm-up regulator with
vacuum compensation for full enrichment, so the
control pressure regulator was deleted.

The control pressure regulator compensates the
enrichment between idle, part and full load.
There is only one way to adjust it.
Attach your fuel pressure gauge and check the control
pressure . You must wait a pair of minutes in
order to get the warm-up regulartor hot.
You shoul read 3.0 bar at idle position, adjust if
not.
The 911 specs book says from 2.9 to 3.1 bar is fine.
1 bar=14.5 psi
Hope this helps,

Gabriel Pennella
sarasa911@yahoo.com

Ed Bighi

Actually, the 1980 911sc had a non-vacuum compensated warm up regulator. The 79 had vaccum and so did the 81 and up, but not the 80.