I have a diesel injector which i need to pull out.Once the top is removed it reveals an internal thread of approx. 18mm,i know because a pinto spark plug bites on the first thread.The thread is finer than that though.Are we talking something odd or regular do you think?

What engine are you working on [Make }

Peugeot 2.0 ltr hdi diesel 16v my good sir

You can get a proper tool for pulling injectors out.