The vehicle runs and drives and most everything works.  There is no light to tell me when the glow plugs have done their job.  I fear the previous owner has done some tampering with various electrical things and maybe the glow plugs are not working at all.   When it is cold, it is harder to start for sure.  Runs great otherwise.   I have only just purchased this older vehicle and I will get the book to study on what to expect.  Found this site.     I am a licensed engineer off ships in the merchant fleet.  I retired here in Panama and there are several of these vehicles here.  I can turn a wrench as needed but I prefer to leave things alone when they are working.  I will change the oil and filters and keep a log of what I do and what I get someone else to do.  I do not trust mechanics in Panama.  I want to become an expert on this vehicle.   Hope to learn from each of you guys.  

Have you checked the fuse or relay for the glow plugs? if the light's not coming on and it's harder to start when cold that might be a point of call?