Bosch part numbers for CIS injectors?

Phil Payne quattro at
Tue Jan 13 16:06:00 EST 2004

> As it happens, a fellow Audi owner had a disconnected 551 F I could
> compare my 551 C with, and they were of equal shape and length downwards
> from the O-ring level. Apparently the 551 C is an older, dropped
> revision of the fine thread injector, and I assume I'll be correct in
> using the Bosch number for 551 F in any further inquiries.

IIRC the "F" is the same as the "C" but has a Viton end seal instead of a metal one.  It

Only comment - "F" injectors, once used, should always be kept in fuel if removed from the
car.  Accurate measurements cannot be made once the injectors have been disconnected for more
than an hour.

  Phil Payne
  +44 7785 302 803

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