How do I test the GP relay. I have a multimeter. The Glow Plugs test as good, but I am getting a rough start after pre-glow. Once engine warms, all is great. Some blue smoke if revved when cold. Also, some pretty strong knocking when cold. I will be adjusting valves with this weekend's oil change. And I would like to get a bead on the source of the poor starts. Thanks.