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soak it with carb cleaner..
work it carefully, if you can get it past all the threads then you could put a blanket over it and crank the engine and maybe blow it out.
the other method is a Glow plug extractor.
IF it is broken off then you might be able to retrieve the pieces by removing the injector.
Kroil has worked on many things that are "stuck"... As @lonewolf_said, if you can work it just a bit, in and out, to let the penetrate get down in the hole. I found that what was holding some of mine was a build up of carbon around the glow plug and not necessarily the glow plug itself... Best to have the engine warm when attempting this. Either run it or plug in the block heater... Every little bit helps... As stated, if you can work it to a point and crank the engine over to let the compression help you out, that is a good thing...
Also read of folks repeatedly hosing with penetrating oil and slowly working one out basically cutting threads into it back and forth while removing.
x3
I would make sure this is done over a few nights throughout the week. Spray it, loosen it, tighten it, repeat as many times as possible. This is the SOP for removing spark plugs from the Triton engines with .0002 spark plug threads in the head. Hopefully it will work for a diesel with swollen GPs. Good luck.
It threads out, then is stuck but wobbles. Engine hasn't ran in 8 years so getting it warm will be difficult. It will crank, so I'll try that.if I pull the injector how do I plug that fuel line?
Don't mess with the injector line once you pull the injector. You can put down a rag on the intake manifold but be safe. That fuel coming out of the injection line is 1800 psi or so!
No need to pull the injector.... One issue at a time.... If it has a block heater, plug it in.... If not, air a torpedo heater at the engine and let it run for an hour... If nothing else, use a hair dryer and just let it sit and warm the area.....
If the glow plug wobbles, there is a good chance most of it is intact.... Just work with it to get some of the carbon to let go and then work it out.... Run some sort of lube / carbon cleaner down around it...
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Triton engines with .0002 spark plug threads in the head. 
Hopefully it will work for a diesel with swollen GPs. Good luck. 
