okay, guys. i'm getting to the bottom of this. it looks like the egr was already disconnected. the line that would normally go from the mechanical switchover to the thermo switch just couples directly to the black vent line that goes through the firewall on the passenger side. meanwhile, there's an extra black line coming from the number 5 position on the mechanical switchover valve that connects to a three way with the other black line coming from the mechanical switch at the number 2 position right before they both enter the vacuum control valve on top of the injection pump.

finally, the white line coming from the number one position on the mechanical switch just connects directly to the front most connector on that little check valve looking thing that sits right on the main line coming from pump. does that all sound right?

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1983 300SD Grey on Grey 220,000 miles

if i'm asking for a part/maintainence/repair information, assume i'm asking about the car above.

1982 240D Manual Trans. RIP