I have a 84 300sd. On top of my vacuum control valve at the injection pump I have one of these
which I think is not only faulty but is the wrong one. Shouldnt I have one of these?
My blue and black valve is oriented black side down. Hooked up to a vac gauge it will allow air to pass from blue to black side but not from black to blue side.
If I understand the vacuum system right then this thing is currently preventing intended vacuum from getting to the vacuum control valve and has been installed upside down. Right?

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.