The allen-head adjustment is mechanical mixture control at the fuel distributor. If the car runs as you say, it can't be too far off, and would not shut off fuel delivery. That would be the job of the EHA on the side of the unit in normal operation. More likely, if the OVP is out and loop control thus disabled, would be a sudden loss of fuel pressure, e.g. bad fuel pump or fuel pump relay. Enrichment at starting via the cold-start valve should only last a few seconds in mild weather.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7