I have checked out my Glow Plug relay and it seems to be working. But the truck does not start. It went form starting easy to no start in one day. If I shoot some ether with wd40 it starts right up and runs with no problem, and will start for the rest of the day. Is there another relay that could be bad? I can't believe all my glow plugs would fail at the same time. I have 160,000 miles on it. Any ideas?