My understanding of EDM is that the "tool" is shaped for the hole you want and it will bore straight down in the shape.

Last time I looked the cross section of a busted glow plug was a resistance electrode encased in ceramic with a metal jacket. Don't know how you're going to to EDM that combination???

A spark eroder in a rudimentary EDM that you can make yourself. Removes broken taps, drills, etc. There used to be plans offered at Lindsay's Books but I don't find them in the current catalog. Google it.

www.lindsaybks.com

CS

Hi Team,
the unit at the dealer was years old and had different Diameter hollow copper tubes depending on the bolt shank size. The head was spring mounted and bouced up and down slightly causing a spark to occur at the end of the rod, this in turn melted the tube and the waste bolt etc., as the head lifted up water would flow and wash out the molten waste metal.
So I guess a shaped tube would work. I think these things have been around for donkeys years as broken threading tap disintegrators.
No doubt today they would have some sort of plasma tooling to do the same thing. Maybe that is the EDM ccjersey is talking about, so I will have to do some checking, just for interest sake.
Cheers,
Eddie B.

If there's ceramic involved, forget the EDM. It only works on materials that conduct electricity. A plasma setup might work but I'd doubt it. .too hard to control as far as depth. Some sort of laser, if depth can be controlled might be the ticket. It would probably be cheaper to get another precup.

I am assuming from the original question, the threaded part of the glowplug screwed out of the chamber leaving the heating tip in place? That doesn't seem very likely, but whatever.

If there are no threads holding it in, what are the chances of punching the remains of the glowplug tip on into the PC chamber where it might be able to be shattered with a punch down through the injector hole/up through the discharge hole/down through the glowplug hole etc. and the remains blown out with compressed air/hooked with a wire and pulled out. Might even be able to get a torch tip close enough to it to torch it if it was still too big.

I think with all the pounding, burning, banging and whatever you may end up with a ruined chamber anyway so I,d look for a new or used chamber to replace it if you can and not keep playing with it.

That takes us back to the original problem.....try and find a glow plug chamber for the D2....they are just about non-existent.

To add to the removal complication is the fact that they are a stepped bore that seats on a bevel where the glow plug body ends and the heating element begins. Not just a straight bore.

As a semi disinterested observer here, as I neither own a D2 nor have even handled one of the offending prechamberers I could be all wrong.

Now, having the disclaimer out of the way. I would think there are only two viable means of removal. It should be possible to disassemble the chamber and punch out the broken stub. Disassembly will require making two fixtures to hold both the top and bottom half of the chamber while it is heated to the point the brazing material liquefies. These fixtures would have to be made of cast iron to prevent inadvertent welding to the chamber.

The second would be to shape a common cold chisel to fit into the bore and use it like a star drill to slowly chop the broken glow plug tip to small enough pieces to allow picking out of the chamber. Lots of tap and turn of the chisel followed by picking small pieces should do it.

seeing as you have two good cups. use for patterns.
Actually they are all good just two you can change the glow plugs.

I see a few of options.
replace them with non glow plug ones. (mine starts without glow plugs)
modify a pair of non glow plug ones to accept glow plugs.
take bad ones apart and remove pieces and re-assemble. (I would at least have two non glow plug ones on hand if things go awry)

Cheers
Dudley