Just another thought since you don't have the manuals. Are you familiar with the priming pump and cold start button?
Thanks for crawling under and taking pics for me. There is a lot more to the 'Z' than I thought. I have no idea about the cold start button. Are you talking about the hand pump right by the injector pump? My tractor has the 3 cylinder diesel and I don't think there is any glow plugs or
I noticed on your tractor you have two hoses coming out from the pump cover, and the third from the drain plug. Is the drain plug hose your return and the other two your 'power' lines? Just scratching my head a little here.