I would unscrew the fitting. If the fitting is filled with sludge, soak it in gasoline, and if you are rich, use carb. cleaner, then wipe clean. Next, use q-tips to clean out the fitting hole or a piece of 14 guage copper wire, bent in a hook, to pull away the sludge. If any loose sludge falls in, fit your vacuum cleaner with a small polypropelene plastic tube (the hard plastic used for water plumbing), and suck out the loose stuff.

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1989 420 SEL