Just snug it up tight enough to firmly(be sensible) compress the Cu washer a bit. Loctite 683 shows "no match" on their website. I've always just screwed the primer pump in and it works and doesn't leak. Great improvement in design over the old style. DON"T stick any sealant down into the IP. Just screw the primer pump in using the Cu washer and you'll be fine.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)