I don't think my glow plugs are working at all. When cold it starts without a problem. When plugged in it starts without a problem. But when left for several hours in the cold, it is extremely hard to start and sometimes it won't start. Is there any way to insure the glow plugs are getting power, without removing the valve covers?

Read Sections 7 and 8 below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281