New Holland 50-86 / Siromer 204S / Case CK-28 / Cat 302.5 / Nissan L35.09 / Nissan Atleon 110
You should see a wire going to one end of the glow plugs (or single glow plug depending upon design). Unplug it from the plug and wrap it well in electrical tape, ensuring it is fastened out of the way (eg: can't get caught in fan belt etc).