I seem to be having the same shutoff valve problem.
I tried the vacuum pump test method and would not hold 100 mbar and would settle down at about 50 mbar.
Then I tried the Sixto method listed above - pushed the stop lever down all the way and the stop pops up half way immediately , then gradually continues it's trip the rest of the way to the run position.

So I need to replace it, and I have found a 602 and 617 DIY on replacing the shut off valve - anyone know of a 603 DIY or is the 602 close enough?

And , is there a true sure-fire way to test if you got the valve in correctly without starting the engine??/?...
Thanks

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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