Thats what your injection pump can look like after 65000 miles of 100% Biodiesel.
No-it's not rust-it's gunk and goo!

VW Golf 1,6l, 54hp pump without LDA:
Could it be moved to the fuel thread ? I think it's more fuel related than IP tech???

 

Wow id hate to take a core apart that looked like that

 

that doesn't look good at all

 

We just opened it, because of a leaky seal.
After 2 hours with all parts thrown into industrial cleaner all parts looked as new and were movable again.
Sad thing is that goo was so sticky, that it could be only removed with a scraper knife.
which in return blocks all internal moving parts.
But as already said after the hot tank everything was ok.