Injectors leaking mid-body.

[nick]

I just rebuilt my injectors with new nozzles and I precisely lapped all the mating surfaces. Two of my injectors are leaking at the nozzle holder to injector interface. I'm pretty sure that the "seal" here is via the threads.

Has anyone had trouble getting injectors to seal mid body?

[Jason]

Sounds like your lapping didn't work out so well.... The threads don't seal anything. The seal is metal to metal at the injector top, intermediate plate, and nozzle surfaces. Usually its the intermediate plate that gets pounded, I would use another one or try to lap it again. Sometimes I have gotten them to seal up just by loosing them and retorqeing the inector body a few times over.

Jason

[ngoma]

x2^

They seal not via the threads, but rather via the precisely machined mating surfaces of the nozzle, nozzle holder, ridged/cupped "washer" piece. Since you "precisely lapped all the mating surfaces," maybe a piece of dirt or foreign material is trapped on one of the sealing surfaces? Try dismantling and meticulously cleaning them, maintaining clean-room conditions during reassembly. In my experience, the ledges in the nozzle holder are the hardest to clean and verify. Using a loupe and strong light helps.