No.2 injector on my Perkins Prima engine started blowing round the injector - not terribly badly, but I thought I'd better fix it. It was the same barrel that had a hydraulic lock when the head gasket went, so it was probably set off by that unsettling the injector. Kind bloke at the diesel place gave me a couple of washers.
Amazingly - I got the injector out in about three minutes - about a fiftieth of what I was expecing. Trouble is I couldn't get the old copper washer out. In the end I ground down a flat woodcutting bit so the lead-spike fitted in the hold in the middle and gently resurfaced the old washer turning the drill by hand. This seems to have worked, there's no blowing now.
What I want to know is, how on earth are you supposed to get the sodding things out anyway? If it'd been damaged I'd have been stuck.