Just because Rectalseal is used in spacecrafts does not automatically warrant it's use in an injection pump system.

I don't recall anywhere in the FSM where a threaded fuel fitting sealed by a copper or aluminum washer calls for pipe dope sealant. I don't understand why Bosch would make an exception in the lift pump. Can you post a copy of the instructions?

No matter how careful you are in applying the pipe dope, the concern is during subsequent R&R where the dope will be disturbed and fall in. The lift pump is not in a very accessible location for cleaning. How do you plan to clean it out? Take the lift pump off? That is more work than I'd want to do.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked