Someone correct me if I'm wrong but it should be open unless overboost tells the valve to close, limiting fuel to the pump. My valve had a small amount of crud in it, took it off the firewall and shot brake cleaner thru it and it cleaned up OK.
Jerry

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Jerry -
If you don't learn something new every day, you aren't paying attention!!
1971 108 280SE 2.8 "Ronnie"
1985 300TDT (76,904 Original miles ) "Sadie" (Sold-went back to Arkansas)
1984 300DT "Green-go" (Sold)
1984 300DT "Silver Bullet" (Sold)
1956 220S Ponton
1985 300D (Sold)
1984 300D