To update.Yes. I don't have any though. All I did for manual glow plug on my first 1985 was to unplug the controller. Then I ran a powered wire through a push button and to the purple wire on the glow plug relay that's on the passenger's side fenderwell. It looks similar to the starter solenoid on the fender. My current 1985 already had a manual control for the glow plugs when I bought it. Not only is the controller wiring not plugged in, the 7.3 that I have in it now has a plug in the port on the head so there's no controller at all. The wiring just hangs there close to the firewall.
I took the glow plugs out they all were Beru Germany. Maybe original? They weren’t broken and looked good overall.
I’ll be doing the compression test soon. All the GP’s need to be out to perform test right? Can the engine be cold?
Also the injectors look to be replaced at some point. They are Delphi.