I am not sure but I think 420sel, being a Gas engine, does not have a screen, neither vacuum pump as a source. The vaccum source is the intake manifold, I believe. It has a vacuum pump under the rear seat but it is for the door locks. The vacuum pump and screen in the engine bay is for the Diesels only.
What kind of problem you are having John.
87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)